diff --git a/.travis.yml b/.travis.yml
index 3cbab23e3c..99fb99af96 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,14 +1,12 @@
 language: ruby
 
-services: mongodb
-
 bundler_args: --without development
 
 rvm:
   - 1.9.3
   - 2.0.0
-  - 2.1
-  - 2.2
+  - 2.1.5
+  - 2.2.0
   - jruby
 
 gemfile:
@@ -16,9 +14,20 @@ gemfile:
   - gemfiles/rails41.gemfile
   - gemfiles/rails42.gemfile
 
-env: JRUBY_OPTS="--server -J-Xms512m -J-Xmx1024m"
+env:
+  global:
+    - CI="travis"
+    - JRUBY_OPTS="--server -J-Xms512m -J-Xmx1024m"
+  matrix:
+    - MONGODB=2.4.14
+    - MONGODB=2.6.10
+    - MONGODB=3.0.3
 
-sudo: false
+before_script:
+  - wget http://fastdl.mongodb.org/linux/mongodb-linux-x86_64-${MONGODB}.tgz -O /tmp/mongodb.tgz
+  - tar -xvf /tmp/mongodb.tgz
+  - mkdir /tmp/data
+  - ${PWD}/mongodb-linux-x86_64-${MONGODB}/bin/mongod --dbpath /tmp/data --bind_ip 127.0.0.1 --auth &> /dev/null &
 
 notifications:
   email: false
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 73d174aafa..b92228eda8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,7 +3,19 @@
 For instructions on upgrading to newer versions, visit
 [mongoid.org](http://mongoid.org/en/mongoid/docs/upgrading.html).
 
-## 4.0.3 - Not released
+## 5.0.0 - Not released
+
+### Major Changes (Backwards Incompatible)
+
+* Mongoid now uses the official Mongo Ruby Driver 2.x instead of Moped.
+
+* Most driver specific configuration options have changed, please see [here](http://docs.mongodb.org/ecosystem/tutorial/ruby-driver-tutorial/#ruby-options) for the new options.
+
+* `find_and_modify` has been removed and replaced with 3 options: `find_one_and_update`, `find_one_and_delete` and `find_one_and_replace`.
+
+* `text_search` has been removed as it is now a `$text` option in a query from 2.6 on.
+
+* Mongoid no longer supports MongoDB 2.2 - support is now for only 2.4 and higher.
 
 ### New Features
 
diff --git a/Gemfile b/Gemfile
index efe47aff3b..de0ff3fbf8 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,4 +1,5 @@
 source "https://rubygems.org"
+
 gemspec
 
 gem "rake"
diff --git a/gemfiles/rails41.gemfile b/gemfiles/rails41.gemfile
index 0fe69f4c48..7b076e9003 100644
--- a/gemfiles/rails41.gemfile
+++ b/gemfiles/rails41.gemfile
@@ -1,6 +1,7 @@
 source "https://rubygems.org"
 gemspec path: '..'
 
+gem "mongo", :github => "mongodb/mongo-ruby-driver"
 gem "rake"
 gem "actionpack",  "~> 4.1.8"
 gem "activemodel", "~> 4.1.8"
diff --git a/gemfiles/rails42.gemfile b/gemfiles/rails42.gemfile
index d29c3433b7..24b146438e 100644
--- a/gemfiles/rails42.gemfile
+++ b/gemfiles/rails42.gemfile
@@ -1,6 +1,7 @@
 source "https://rubygems.org"
 gemspec path: '..'
 
+gem "mongo", :github => "mongodb/mongo-ruby-driver"
 gem "rake"
 gem "actionpack",  "~> 4.2.0"
 gem "activemodel", "~> 4.2.0"
diff --git a/lib/mongoid.rb b/lib/mongoid.rb
index befb3a0806..88da6e0f41 100644
--- a/lib/mongoid.rb
+++ b/lib/mongoid.rb
@@ -13,14 +13,13 @@
 require "active_model"
 
 require "origin"
-require "moped"
+require "mongo"
 
 require "mongoid/version"
 require "mongoid/config"
 require "mongoid/loggable"
 require "mongoid/sessions"
 require "mongoid/document"
-require "mongoid/log_subscriber"
 require "mongoid/tasks/database"
 require "mongoid/query_cache"
 
diff --git a/lib/mongoid/config.rb b/lib/mongoid/config.rb
index 088c7746ff..09e2377e56 100644
--- a/lib/mongoid/config.rb
+++ b/lib/mongoid/config.rb
@@ -48,7 +48,7 @@ def configured?
     # @param [ String ] name The database name.
     #
     # @since 3.0.0
-    def connect_to(name, options = { read: :primary })
+    def connect_to(name, options = { read: { mode: :primary }})
       self.sessions = {
         default: {
           database: name,
@@ -169,7 +169,7 @@ def override_session(name)
     #
     # @since 2.0.2
     def purge!
-      Sessions.default.collections.each(&:drop) and true
+      Sessions.default.database.collections.each(&:drop) and true
     end
 
     # Truncate all data in all collections, but not the indexes.
@@ -183,8 +183,8 @@ def purge!
     #
     # @since 2.0.2
     def truncate!
-      Sessions.default.collections.each do |collection|
-        collection.find.remove_all
+      Sessions.default.database.collections.each do |collection|
+        collection.find.delete_many
       end and true
     end
 
@@ -217,22 +217,6 @@ def sessions
       @sessions ||= {}
     end
 
-    # Set the session configuration options.
-    #
-    # @example Set the session configuration options.
-    #   config.sessions = { default: { hosts: [ "localhost:27017" ] }}
-    #
-    # @param [ Hash ] sessions The configuration options.
-    #
-    # @since 3.0.0
-    def sessions=(sessions)
-      raise Errors::NoSessionsConfig.new unless sessions
-      sess = sessions.with_indifferent_access
-      Validators::Session.validate(sess)
-      @sessions = sess
-      sess
-    end
-
     # Get the time zone to use.
     #
     # @example Get the time zone.
@@ -256,5 +240,15 @@ def time_zone
     def running_with_passenger?
       @running_with_passenger ||= defined?(PhusionPassenger)
     end
+
+    private
+
+    def sessions=(sessions)
+      raise Errors::NoSessionsConfig.new unless sessions
+      sess = sessions.with_indifferent_access
+      Validators::Session.validate(sess)
+      @sessions = sess
+      sess
+    end
   end
 end
diff --git a/lib/mongoid/contextual/aggregable/mongo.rb b/lib/mongoid/contextual/aggregable/mongo.rb
index 5ad601974c..560602fbee 100644
--- a/lib/mongoid/contextual/aggregable/mongo.rb
+++ b/lib/mongoid/contextual/aggregable/mongo.rb
@@ -23,7 +23,7 @@ module Mongo
         #
         # @since 3.0.0
         def aggregates(field)
-          result = collection.aggregate(pipeline(field)).to_a
+          result = collection.find.aggregate(pipeline(field)).to_a
           if result.empty?
             { "count" => 0, "sum" => nil, "avg" => nil, "min" => nil, "max" => nil }
           else
diff --git a/lib/mongoid/contextual/atomic.rb b/lib/mongoid/contextual/atomic.rb
index 31c073cc1b..b859867798 100644
--- a/lib/mongoid/contextual/atomic.rb
+++ b/lib/mongoid/contextual/atomic.rb
@@ -14,7 +14,7 @@ module Atomic
       #
       # @since 3.0.0
       def add_to_set(adds)
-        query.update_all("$addToSet" => collect_operations(adds))
+        view.update_many("$addToSet" => collect_operations(adds))
       end
 
       # Perform an atomic $bit operation on the matching documents.
@@ -28,7 +28,7 @@ def add_to_set(adds)
       #
       # @since 3.0.0
       def bit(bits)
-        query.update_all("$bit" => collect_operations(bits))
+        view.update_many("$bit" => collect_operations(bits))
       end
 
       # Perform an atomic $inc operation on the matching documents.
@@ -42,7 +42,7 @@ def bit(bits)
       #
       # @since 3.0.0
       def inc(incs)
-        query.update_all("$inc" => collect_operations(incs))
+        view.update_many("$inc" => collect_operations(incs))
       end
 
       # Perform an atomic $pop operation on the matching documents.
@@ -59,7 +59,7 @@ def inc(incs)
       #
       # @since 3.0.0
       def pop(pops)
-        query.update_all("$pop" => collect_operations(pops))
+        view.update_many("$pop" => collect_operations(pops))
       end
 
       # Perform an atomic $pull operation on the matching documents.
@@ -75,7 +75,7 @@ def pop(pops)
       #
       # @since 3.0.0
       def pull(pulls)
-        query.update_all("$pull" => collect_operations(pulls))
+        view.update_many("$pull" => collect_operations(pulls))
       end
 
       # Perform an atomic $pullAll operation on the matching documents.
@@ -89,7 +89,7 @@ def pull(pulls)
       #
       # @since 3.0.0
       def pull_all(pulls)
-        query.update_all("$pullAll" => collect_operations(pulls))
+        view.update_many("$pullAll" => collect_operations(pulls))
       end
 
       # Perform an atomic $push operation on the matching documents.
@@ -103,7 +103,7 @@ def pull_all(pulls)
       #
       # @since 3.0.0
       def push(pushes)
-        query.update_all("$push" => collect_operations(pushes))
+        view.update_many("$push" => collect_operations(pushes))
       end
 
       # Perform an atomic $pushAll operation on the matching documents.
@@ -117,7 +117,7 @@ def push(pushes)
       #
       # @since 3.0.0
       def push_all(pushes)
-        query.update_all("$pushAll" => collect_operations(pushes))
+        view.update_many("$pushAll" => collect_operations(pushes))
       end
 
       # Perform an atomic $rename of fields on the matching documents.
@@ -135,7 +135,7 @@ def rename(renames)
           ops[old_name] = new_name.to_s
           ops
         end
-        query.update_all("$rename" => collect_operations(operations))
+        view.update_many("$rename" => collect_operations(operations))
       end
 
       # Perform an atomic $set of fields on the matching documents.
@@ -149,7 +149,7 @@ def rename(renames)
       #
       # @since 3.0.0
       def set(sets)
-        query.update_all("$set" => collect_operations(sets))
+        view.update_many("$set" => collect_operations(sets))
       end
 
       # Perform an atomic $unset of a field on the matching documents.
@@ -164,7 +164,7 @@ def set(sets)
       # @since 3.0.0
       def unset(*args)
         fields = args.__find_args__.collect { |f| [database_field_name(f), true] }
-        query.update_all("$unset" => Hash[fields])
+        view.update_many("$unset" => Hash[fields])
       end
 
       private
diff --git a/lib/mongoid/contextual/command.rb b/lib/mongoid/contextual/command.rb
index 209274149e..2246ace93c 100644
--- a/lib/mongoid/contextual/command.rb
+++ b/lib/mongoid/contextual/command.rb
@@ -28,7 +28,7 @@ def command
       #
       # @since 3.0.0
       def session
-        collection.database.session
+        collection.database.client
       end
     end
   end
diff --git a/lib/mongoid/contextual/find_and_modify.rb b/lib/mongoid/contextual/find_and_modify.rb
deleted file mode 100644
index b0e71cd288..0000000000
--- a/lib/mongoid/contextual/find_and_modify.rb
+++ /dev/null
@@ -1,69 +0,0 @@
-# encoding: utf-8
-module Mongoid
-  module Contextual
-    class FindAndModify
-      include Command
-
-      # @attribute [r] criteria The criteria for the context.
-      # @attribute [r] options The command options.
-      # @attribute [r] update The updates.
-      # @attribute [r] query The Moped query.
-      attr_reader :criteria, :options, :update, :query
-
-      # Initialize the find and modify command, used for MongoDB's
-      # $findAndModify.
-      #
-      # @example Initialize the command.
-      #   FindAndModify.new(criteria, { "$set" => { likes: 1 }})
-      #
-      # @param [ Criteria ] criteria The criteria.
-      # @param [ Hash ] update The updates.
-      # @param [ Hash ] options The command options.
-      #
-      # @option options [ true, false ] :new Return the updated document.
-      # @option options [ true, false ] :remove Delete the first document.
-      # @option options [ true, false ] :upsert Create the document if it doesn't exist.
-      #
-      # @since 3.0.0
-      def initialize(collection, criteria, update, options = {})
-        @collection, @criteria, @options, @update =
-          collection, criteria, options, update.mongoize
-        @query = collection.find(criteria.selector)
-        apply_criteria_options
-      end
-
-      # Get the result of the $findAndModify.
-      #
-      # @example Get the result.
-      #   find_and_modify.result
-      #
-      # @return [ Hash ] The result of the command.
-      #
-      # @since 3.0.0
-      def result
-        query.modify(update, options)
-      end
-
-      private
-
-      # Apply criteria specific options - query, sort, fields.
-      #
-      # @api private
-      #
-      # @example Apply the criteria options
-      #   find_and_modify.apply_criteria_options
-      #
-      # @return [ nil ] Nothing.
-      #
-      # @since 3.0.0
-      def apply_criteria_options
-        if spec = criteria.options[:sort]
-          query.sort(spec)
-        end
-        if spec = criteria.options[:fields]
-          query.select(spec)
-        end
-      end
-    end
-  end
-end
diff --git a/lib/mongoid/contextual/geo_near.rb b/lib/mongoid/contextual/geo_near.rb
index c6c510db29..f94e5bb0d0 100644
--- a/lib/mongoid/contextual/geo_near.rb
+++ b/lib/mongoid/contextual/geo_near.rb
@@ -246,7 +246,7 @@ def documents
       #
       # @since 3.0.0
       def results
-        @results ||= session.command(command)
+        @results ||= session.command(command).first
       end
     end
   end
diff --git a/lib/mongoid/contextual/map_reduce.rb b/lib/mongoid/contextual/map_reduce.rb
index a0da1d46fb..29ebd2853b 100644
--- a/lib/mongoid/contextual/map_reduce.rb
+++ b/lib/mongoid/contextual/map_reduce.rb
@@ -268,9 +268,9 @@ def apply_criteria_options
       # @since 3.0.0
       def documents
         return results["results"] if results.has_key?("results")
-        query = session[output_collection].find
-        query.no_timeout if criteria.options[:timeout] == false
-        query
+        view = session[output_collection].find
+        view.no_cursor_timeout if criteria.options[:timeout] == false
+        view
       end
 
       # Get the collection that the map/reduce results were stored in.
@@ -299,7 +299,7 @@ def output_collection
       # @since 3.0.0
       def results
         raise Errors::NoMapReduceOutput.new(command) unless command[:out]
-        @results ||= __session__.command(command)
+        @results ||= __session__.command(command).first
       end
 
       # Get the session with the proper consistency.
@@ -316,7 +316,7 @@ def results
       # @since 3.0.15
       def __session__
         if command[:out][:inline] != 1
-          session.with(read: :primary)
+          session.with(read: { mode: :primary })
         else
           session
         end
diff --git a/lib/mongoid/contextual/memory.rb b/lib/mongoid/contextual/memory.rb
index 835152cdc2..27be890b57 100644
--- a/lib/mongoid/contextual/memory.rb
+++ b/lib/mongoid/contextual/memory.rb
@@ -47,7 +47,7 @@ def delete
           doc.as_document
         end
         unless removed.empty?
-          collection.find(selector).update(
+          collection.find(selector).update_one(
             positionally(selector, "$pullAll" => { path => removed })
           )
         end
@@ -307,7 +307,7 @@ def update_documents(attributes, docs)
           updates["$set"].merge!(doc.atomic_updates["$set"] || {})
           doc.move_changes
         end
-        collection.find(selector).update(updates) unless updates["$set"].empty?
+        collection.find(selector).update_one(updates) unless updates["$set"].empty?
       end
 
       # Get the limiting value.
diff --git a/lib/mongoid/contextual/mongo.rb b/lib/mongoid/contextual/mongo.rb
index 57bb1509ab..6e6e8c93d4 100644
--- a/lib/mongoid/contextual/mongo.rb
+++ b/lib/mongoid/contextual/mongo.rb
@@ -2,10 +2,8 @@
 require "mongoid/contextual/atomic"
 require "mongoid/contextual/aggregable/mongo"
 require "mongoid/contextual/command"
-require "mongoid/contextual/find_and_modify"
 require "mongoid/contextual/geo_near"
 require "mongoid/contextual/map_reduce"
-require "mongoid/contextual/text_search"
 require "mongoid/relations/eager"
 
 module Mongoid
@@ -17,8 +15,8 @@ class Mongo
       include Relations::Eager
       include Queryable
 
-      # @attribute [r] query The Moped query.
-      attr_reader :query
+      # @attribute [r] view The Mongo collection view.
+      attr_reader :view
 
       # Is the context cached?
       #
@@ -37,27 +35,23 @@ def cached?
       # @example Get the number of matching documents.
       #   context.count
       #
-      # @example Get the count of documents matching the provided.
-      #   context.count(document)
+      # @example Get the count of documents with the provided options.
+      #   context.count(limit: 1)
       #
       # @example Get the count for where the provided block is true.
       #   context.count do |doc|
       #     doc.likes > 1
       #   end
       #
-      # @param [ Document ] document A document to match or true if wanting
-      #   skip and limit to be factored into the count.
+      # @param [ Hash ] options The options, such as skip and limit to be factored
+      #   into the count.
       #
       # @return [ Integer ] The number of matches.
       #
       # @since 3.0.0
-      def count(document = false, &block)
+      def count(options = {}, &block)
         return super(&block) if block_given?
-        if document.is_a?(Document)
-          return collection.find(criteria.and(_id: document._id).selector).count
-        end
-        return query.count(document) if document
-        try_cache(:count) { query.count }
+        try_cache(:count) { view.count(options) }
       end
 
       # Delete all documents in the database that match the selector.
@@ -70,7 +64,7 @@ def count(document = false, &block)
       # @since 3.0.0
       def delete
         self.count.tap do
-          query.remove_all
+          view.delete_many
         end
       end
       alias :delete_all :delete
@@ -103,7 +97,7 @@ def destroy
       #
       # @since 3.0.0
       def distinct(field)
-        query.distinct(klass.database_field_name(field))
+        view.distinct(klass.database_field_name(field))
       end
 
       # Iterate over the context. If provided a block, yield to a Mongoid
@@ -146,7 +140,7 @@ def exists?
         return @count > 0 if instance_variable_defined?(:@count)
 
         try_cache(:exists) do
-          !!(query.dup.select(_id: 1).limit(1).first)
+          !!(view.projection(_id: 1).limit(1).first)
         end
       end
 
@@ -159,28 +153,65 @@ def exists?
       #
       # @since 3.0.0
       def explain
-        query.explain
+        view.explain
       end
 
       # Execute the find and modify command, used for MongoDB's
       # $findAndModify.
       #
       # @example Execute the command.
-      #   context.find_and_modify({ "$inc" => { likes: 1 }}, new: true)
+      #   context.find_one_and_update({ "$inc" => { likes: 1 }})
       #
       # @param [ Hash ] update The updates.
       # @param [ Hash ] options The command options.
       #
-      # @option options [ true, false ] :new Return the updated document.
-      # @option options [ true, false ] :remove Delete the first document.
+      # @option options [ :before, :after ] :return_document Return the updated document
+      #   from before or after update.
       # @option options [ true, false ] :upsert Create the document if it doesn't exist.
       #
       # @return [ Document ] The result of the command.
       #
-      # @since 3.0.0
-      def find_and_modify(update, options = {})
-        if doc = FindAndModify.new(collection, criteria, update, options).result
-          Factory.from_db(klass, doc) if doc.any?
+      # @since 5.0.0
+      def find_one_and_update(update, options = {})
+        if doc = view.find_one_and_update(update, options)
+          Factory.from_db(klass, doc)
+        end
+      end
+
+      # Execute the find and modify command, used for MongoDB's
+      # $findAndModify.
+      #
+      # @example Execute the command.
+      #   context.find_one_and_update({ likes: 1 })
+      #
+      # @param [ Hash ] update The updates.
+      # @param [ Hash ] options The command options.
+      #
+      # @option options [ :before, :after ] :return_document Return the updated document
+      #   from before or after update.
+      # @option options [ true, false ] :upsert Create the document if it doesn't exist.
+      #
+      # @return [ Document ] The result of the command.
+      #
+      # @since 5.0.0
+      def find_one_and_replace(replacement, options = {})
+        if doc = view.find_one_and_replace(replacement, options)
+          Factory.from_db(klass, doc)
+        end
+      end
+
+      # Execute the find and modify command, used for MongoDB's
+      # $findAndModify. This deletes the found document.
+      #
+      # @example Execute the command.
+      #   context.find_one_and_delete
+      #
+      # @return [ Document ] The result of the command.
+      #
+      # @since 5.0.0
+      def find_one_and_delete
+        if doc = view.find_one_and_delete
+          Factory.from_db(klass, doc)
         end
       end
 
@@ -196,7 +227,7 @@ def first
         return documents.first if cached? && cache_loaded?
         try_cache(:first) do
           with_sorting do
-            with_eager_loading(query.first)
+            with_eager_loading(view.first)
           end
         end
       end
@@ -209,7 +240,7 @@ def first
       # @since 4.0.2
       def find_first
         return documents.first if cached? && cache_loaded?
-        with_eager_loading(query.first)
+        with_eager_loading(view.first)
       end
 
       # Execute a $geoNear command against the database.
@@ -272,7 +303,7 @@ def initialize(criteria)
         @criteria, @klass, @cache = criteria, criteria.klass, criteria.options[:cache]
         @collection = @klass.with(criteria.persistence_options || {}).collection
         criteria.send(:merge_type_selection)
-        @query = collection.find(criteria.selector)
+        @view = collection.find(criteria.selector)
         apply_options
       end
 
@@ -289,7 +320,7 @@ def initialize(criteria)
       def last
         try_cache(:last) do
           with_inverse_sorting do
-            with_eager_loading(query.first)
+            with_eager_loading(view.first)
           end
         end
       end
@@ -318,7 +349,7 @@ def length
       #
       # @since 3.0.0
       def limit(value)
-        query.limit(value) and self
+        @view = view.limit(value) and self
       end
 
       # Initiate a map/reduce operation from the context.
@@ -356,7 +387,7 @@ def pluck(*fields)
           hash
         end
 
-        query.dup.select(normalized_select).map do |doc|
+        view.projection(normalized_select).map do |doc|
           if normalized_select.size == 1
             doc[normalized_select.keys.first]
           else
@@ -376,7 +407,7 @@ def pluck(*fields)
       #
       # @since 3.0.0
       def skip(value)
-        query.skip(value) and self
+        @view = view.skip(value) and self
       end
 
       # Sorts the documents by the provided spec.
@@ -401,20 +432,6 @@ def sort(values = nil, &block)
         end
       end
 
-      # Execute a text command against the database.
-      #
-      # @example Find documents with the text "phase"
-      #   context.text_search("phase")
-      #
-      # @param [ String ] query The text search query.
-      #
-      # @return [ TextSearch ] The TextSearch command.
-      #
-      # @since 4.0.0
-      def text_search(query)
-        TextSearch.new(collection, criteria, query)
-      end
-
       # Update the first matching document atomically.
       #
       # @example Update the first matching document.
@@ -440,7 +457,7 @@ def update(attributes = nil)
       #
       # @since 3.0.0
       def update_all(attributes = nil)
-        update_documents(attributes, :update_all)
+        update_documents(attributes, :update_many)
       end
 
       private
@@ -476,10 +493,10 @@ def try_cache(key, &block)
       # @return [ true, false ] If the update succeeded.
       #
       # @since 3.0.4
-      def update_documents(attributes, method = :update)
+      def update_documents(attributes, method = :update_one)
         return false unless attributes
         attributes = Hash[attributes.map { |k, v| [klass.database_field_name(k.to_s), v] }]
-        query.send(method, attributes.__consolidate__(klass))
+        view.send(method, attributes.__consolidate__(klass))
       end
 
       # Apply the field limitations.
@@ -492,7 +509,7 @@ def update_documents(attributes, method = :update)
       # @since 3.0.0
       def apply_fields
         if spec = criteria.options[:fields]
-          query.select(spec)
+          @view = view.projection(spec)
         end
       end
 
@@ -510,7 +527,7 @@ def apply_options
           apply_option(name)
         end
         if criteria.options[:timeout] == false
-          query.no_timeout
+          @view = view.no_cursor_timeout
         end
       end
 
@@ -524,7 +541,7 @@ def apply_options
       # @since 3.1.0
       def apply_option(name)
         if spec = criteria.options[name]
-          query.send(name, spec)
+          @view = view.send(name, spec)
         end
       end
 
@@ -540,7 +557,7 @@ def apply_option(name)
       def with_sorting
         begin
           unless criteria.options.has_key?(:sort)
-            query.sort(_id: 1)
+            @view = view.sort(_id: 1)
           end
           yield
         ensure
@@ -559,9 +576,9 @@ def with_sorting
       def with_inverse_sorting
         begin
           if spec = criteria.options[:sort]
-            query.sort(Hash[spec.map{|k, v| [k, -1*v]}])
+            @view = view.sort(Hash[spec.map{|k, v| [k, -1*v]}])
           else
-            query.sort(_id: -1)
+            @view = view.sort(_id: -1)
           end
           yield
         ensure
@@ -632,11 +649,11 @@ def documents_for_iteration
         if cached? && !documents.empty?
           documents
         elsif eager_loadable?
-          docs = query.map{ |doc| Factory.from_db(klass, doc, criteria.options[:fields]) }
+          docs = view.map{ |doc| Factory.from_db(klass, doc, criteria.options[:fields]) }
           eager_load(docs)
           docs
         else
-          query
+          view
         end
       end
 
diff --git a/lib/mongoid/contextual/text_search.rb b/lib/mongoid/contextual/text_search.rb
deleted file mode 100644
index 1e5677118b..0000000000
--- a/lib/mongoid/contextual/text_search.rb
+++ /dev/null
@@ -1,178 +0,0 @@
-# encoding: utf-8
-module Mongoid
-  module Contextual
-
-    # Wraps behaviour around a lazy text search command.
-    #
-    # @since 4.0.0
-    class TextSearch
-      include Enumerable
-      include Command
-
-      delegate :[], to: :results
-      delegate :==, :empty?, to: :entries
-
-      # Iterate over the results of the text search command.
-      #
-      # @example Iterate over the results.
-      #   text_search.each do |doc|
-      #     #...
-      #   end
-      #
-      # @return [ Enumerator ] The enumerator.
-      #
-      # @since 4.0.0
-      def each
-        if block_given?
-          documents.each do |doc|
-            yield doc
-          end
-        else
-          to_enum
-        end
-      end
-
-      # Instantiate a new text search lazy proxy.
-      #
-      # @example Instantiate the text search.
-      #   TextSearch.new(collection, criteria, "test")
-      #
-      # @param [ Moped::Collection ] collection The collection to execute on.
-      # @param [ Criteria ] criteria The criteria to filter results.
-      # @param [ String ] search_string The search string.
-      #
-      # @since 4.0.0
-      def initialize(collection, criteria, search_string)
-        @collection, @criteria = collection, criteria
-        command[:text] = collection.name.to_s
-        command[:search] = search_string
-        apply_criteria_options
-      end
-
-      # Inspect the text search object.
-      #
-      # @example Inspect the text search.
-      #   text_search.inspect
-      #
-      # @return [ String ] The inspection.
-      #
-      # @since 4.0.0
-      def inspect
-%Q{#<Mongoid::Contextual::TextSearch
-  selector:   #{criteria.selector.inspect}
-  class:      #{criteria.klass}
-  search:     #{command[:search]}
-  filter:     #{command[:filter] || "N/A"}
-  project:    #{command[:project] || "N/A"}
-  limit:      #{command[:limit] || "N/A"}
-  language:   #{command[:language] || "default"}>
-}
-      end
-
-      # Execute the text search command, and return the raw results (in hash
-      # form).
-      #
-      # @example Execute the command.
-      #   text_search.execute
-      #
-      # @return [ Hash ] The raw results.
-      #
-      # @since 4.0.0
-      def execute
-        results
-      end
-
-      # Set the language of the text search.
-      #
-      # @example Set the text search language.
-      #   text_search.language("deutsch")
-      #
-      # @param [ String ] value The name of the language.
-      #
-      # @return [ TextSearch ] The modified text search.
-      #
-      # @since 4.0.0
-      def language(value)
-        command[:language] = value
-        self
-      end
-
-      # Limits the fields returned by the text search for each document. By
-      # default, _id is always included.
-      #
-      # @example Limit the returned fields.
-      #   text_search.project(name: 1, title: 1)
-      #
-      # @param [ Hash ] value The fields to project.
-      #
-      # @return [ TextSearch ] The modified text search.
-      #
-      # @since 4.0.0
-      def project(value)
-        command[:project] = value
-        self
-      end
-
-      # Get the raw statistics returned from the text search.
-      #
-      # @example Get the stats.
-      #   text_search.stats
-      #
-      # @return [ Hash ] The raw statistics.
-      #
-      # @since 4.0.0
-      def stats
-        results["stats"]
-      end
-
-      private
-
-      # Apply the options from the criteria to the text search command.
-      #
-      # @api private
-      #
-      # @example Apply the criteria options, filter and limit only.
-      #   text_search.apply_criteria_options
-      #
-      # @return [ nil ] Nothing.
-      #
-      # @since 4.0.0
-      def apply_criteria_options
-        command[:filter] = criteria.selector
-        if limit = criteria.options[:limit]
-          command[:limit] = limit
-        end
-      end
-
-      # Get the results of the text search as documents.
-      #
-      # @api private
-      #
-      # @example Get the results as documents.
-      #   text_search.documents
-      #
-      # @return [ Array<Document> ] The documents.
-      #
-      # @since 4.0.0
-      def documents
-        results["results"].map do |attributes|
-          Factory.from_db(criteria.klass, attributes["obj"], command[:project])
-        end
-      end
-
-      # Get the raw results.
-      #
-      # @api private
-      #
-      # @example Get the raw results.
-      #   text_search.results
-      #
-      # @return [ Hash ] The raw results.
-      #
-      # @since 4.0.0
-      def results
-        @results ||= session.command(command)
-      end
-    end
-  end
-end
diff --git a/lib/mongoid/findable.rb b/lib/mongoid/findable.rb
index 824c33200b..02657e6884 100644
--- a/lib/mongoid/findable.rb
+++ b/lib/mongoid/findable.rb
@@ -19,7 +19,9 @@ module Findable
       :each,
       :each_with_index,
       :extras,
-      :find_and_modify,
+      :find_one_and_delete,
+      :find_one_and_replace,
+      :find_one_and_update,
       :find_or_create_by,
       :find_or_create_by!,
       :find_or_initialize_by,
diff --git a/lib/mongoid/indexable.rb b/lib/mongoid/indexable.rb
index dc0af6b977..a6c1c6d883 100644
--- a/lib/mongoid/indexable.rb
+++ b/lib/mongoid/indexable.rb
@@ -31,10 +31,10 @@ def create_indexes
         index_specifications.each do |spec|
           key, options = spec.key, spec.options
           if database = options[:database]
-            with(read: :primary, database: database).
-              collection.indexes.create(key, options.except(:database))
+            with(read: { mode: :primary }, database: database).
+              collection.indexes.create_one(key, options.except(:database))
           else
-            with(read: :primary).collection.indexes.create(key, options)
+            with(read: { mode: :primary }).collection.indexes.create_one(key, options)
           end
         end and true
       end
@@ -50,12 +50,14 @@ def create_indexes
       # @since 3.0.0
       def remove_indexes
         indexed_database_names.each do |database|
-          collection = with(read: :primary, database: database).collection
-          collection.indexes.each do |spec|
-            unless spec["name"] == "_id_"
-              collection.indexes.drop(spec["key"])
+          collection = with(read: { mode: :primary }, database: database).collection
+          begin
+            collection.indexes.each do |spec|
+              unless spec["name"] == "_id_"
+                collection.indexes.drop_one(spec["key"])
+              end
             end
-          end
+          rescue Mongo::Error::OperationFailure; end
         end and true
       end
 
diff --git a/lib/mongoid/log_subscriber.rb b/lib/mongoid/log_subscriber.rb
deleted file mode 100644
index 9493da2dc9..0000000000
--- a/lib/mongoid/log_subscriber.rb
+++ /dev/null
@@ -1,55 +0,0 @@
-# encoding: utf-8
-module Mongoid
-  # A Log subscriber to the moped queries
-  #
-  # @since 4.0.0
-  class LogSubscriber < ActiveSupport::LogSubscriber
-
-    # Log the query operation on moped
-    #
-    # @since 4.0.0
-    def query(event)
-      return unless logger.debug?
-
-      payload = event.payload
-      runtime = ("%.4fms" % event.duration)
-      debug(payload[:prefix], payload[:ops], runtime)
-    end
-
-    def query_cache(event)
-      return unless logger.debug?
-
-      database, collection, selector = event.payload[:key]
-      operation = "%-12s database=%s collection=%s selector=%s" % ["QUERY CACHE", database, collection, selector.inspect]
-      logger.debug operation
-    end
-    # Log the provided operations.
-    #
-    # @example Delegates the operation to moped so it can log it.
-    #   subscriber.debug("MOPED", {}, 30)
-    #
-    # @param [ String ] prefix The prefix for all operations in the log.
-    # @param [ Array ] ops The operations.
-    # @param [ String ] runtime The runtime in formatted ms.
-    #
-    # @since 4.0.0
-    def debug(prefix, operations, runtime)
-      Moped::Loggable.log_operations(prefix, operations, runtime)
-    end
-
-    # Get the logger.
-    #
-    # @example Get the logger.
-    #   subscriber.logger
-    #
-    # @return [ Logger ] The logger.
-    #
-    # @since 4.0.0
-    def logger
-      Moped.logger
-    end
-  end
-end
-
-Mongoid::LogSubscriber.attach_to :moped
-Mongoid::LogSubscriber.attach_to :mongoid
diff --git a/lib/mongoid/persistable.rb b/lib/mongoid/persistable.rb
index a846b87025..16e52ddcd6 100644
--- a/lib/mongoid/persistable.rb
+++ b/lib/mongoid/persistable.rb
@@ -209,7 +209,7 @@ def persist_or_delay_atomic_operation(operation)
     def persist_atomic_operations(operations)
       if persisted?
         selector = atomic_selector
-        _root.collection.find(selector).update(positionally(selector, operations))
+        _root.collection.find(selector).update_one(positionally(selector, operations))
       end
     end
   end
diff --git a/lib/mongoid/persistable/creatable.rb b/lib/mongoid/persistable/creatable.rb
index 1d5501753e..afbe23c780 100644
--- a/lib/mongoid/persistable/creatable.rb
+++ b/lib/mongoid/persistable/creatable.rb
@@ -61,7 +61,7 @@ def insert_as_embedded
           _parent.insert
         else
           selector = _parent.atomic_selector
-          _root.collection.find(selector).update(positionally(selector, atomic_inserts))
+          _root.collection.find(selector).update_one(positionally(selector, atomic_inserts))
         end
       end
 
@@ -76,7 +76,7 @@ def insert_as_embedded
       #
       # @since 4.0.0
       def insert_as_root
-        collection.insert(as_document)
+        collection.insert_one(as_document)
       end
 
       # Post process an insert, which sets the new record attribute to false
diff --git a/lib/mongoid/persistable/deletable.rb b/lib/mongoid/persistable/deletable.rb
index 1f58ca3d0f..cd227f8763 100644
--- a/lib/mongoid/persistable/deletable.rb
+++ b/lib/mongoid/persistable/deletable.rb
@@ -62,7 +62,7 @@ def delete_as_embedded(options = {})
         _parent.remove_child(self) if notifying_parent?(options)
         if _parent.persisted?
           selector = _parent.atomic_selector
-          _root.collection.find(selector).update(positionally(selector, atomic_deletes))
+          _root.collection.find(selector).update_one(positionally(selector, atomic_deletes))
         end
         true
       end
@@ -78,7 +78,7 @@ def delete_as_embedded(options = {})
       #
       # @since 4.0.0
       def delete_as_root
-        collection.find(atomic_selector).remove
+        collection.find(atomic_selector).delete_one
         true
       end
 
@@ -140,7 +140,7 @@ def delete_all(conditions = nil)
           selector.merge!(_type: name) if hereditary?
           coll = collection
           deleted = coll.find(selector).count
-          coll.find(selector).remove_all
+          coll.find(selector).delete_many
           deleted
         end
       end
diff --git a/lib/mongoid/persistable/updatable.rb b/lib/mongoid/persistable/updatable.rb
index 1633c1cc24..b995f8f052 100644
--- a/lib/mongoid/persistable/updatable.rb
+++ b/lib/mongoid/persistable/updatable.rb
@@ -141,9 +141,9 @@ def update_document(options = {})
           unless updates.empty?
             coll = _root.collection
             selector = atomic_selector
-            coll.find(selector).update(positionally(selector, updates))
+            coll.find(selector).update_one(positionally(selector, updates))
             conflicts.each_pair do |key, value|
-              coll.find(selector).update(positionally(selector, { key => value }))
+              coll.find(selector).update_one(positionally(selector, { key => value }))
             end
           end
         end
diff --git a/lib/mongoid/persistable/upsertable.rb b/lib/mongoid/persistable/upsertable.rb
index 3a606b8b3b..175878d2a5 100644
--- a/lib/mongoid/persistable/upsertable.rb
+++ b/lib/mongoid/persistable/upsertable.rb
@@ -21,7 +21,7 @@ module Upsertable
       # @since 3.0.0
       def upsert(options = {})
         prepare_upsert(options) do
-          collection.find(atomic_selector).update(as_document, [ :upsert ])
+          collection.find(atomic_selector).update_one(as_document, upsert: true)
         end
       end
 
diff --git a/lib/mongoid/query_cache.rb b/lib/mongoid/query_cache.rb
index d1cb7a72d3..2198c4e419 100644
--- a/lib/mongoid/query_cache.rb
+++ b/lib/mongoid/query_cache.rb
@@ -107,149 +107,143 @@ def call(env)
       end
     end
 
-    module Base # :nodoc:
-
-      def alias_query_cache_clear(*method_names)
-        method_names.each do |method_name|
-          class_eval <<-CODE, __FILE__, __LINE__ + 1
-              def #{method_name}_with_clear_cache(*args)   # def upsert_with_clear_cache(*args)
-                QueryCache.clear_cache                     #   QueryCache.clear_cache
-                #{method_name}_without_clear_cache(*args)  #   upsert_without_clear_cache(*args)
-              end                                          # end
-            CODE
+    # A Cursor that attempts to load documents from memory first before hitting
+    # the database if the same query has already been executed.
+    #
+    # @since 5.0.0
+    class CachedCursor < Mongo::Cursor
 
-          alias_method_chain method_name, :clear_cache
+      # We iterate over the cached documents if they exist already in the
+      # cursor otherwise proceed as normal.
+      #
+      # @example Iterate over the documents.
+      #   cursor.each do |doc|
+      #     # ...
+      #   end
+      #
+      # @since 5.0.0
+      def each
+        if @cached_documents
+          @cached_documents.each{ |doc| yield doc }
+        else
+          super
         end
       end
+
+      # Get a human-readable string representation of +Cursor+.
+      #
+      # @example Inspect the cursor.
+      #   cursor.inspect
+      #
+      # @return [ String ] A string representation of a +Cursor+ instance.
+      #
+      # @since 2.0.0
+      def inspect
+        "#<Mongoid::QueryCache::CachedCursor:0x#{object_id} @view=#{@view.inspect}>"
+      end
+
+      private
+
+      def process(result)
+        @remaining -= result.returned_count if limited?
+        @cursor_id = result.cursor_id
+        @coll_name ||= result.namespace.sub("#{database.name}.", '') if result.namespace
+        documents = result.documents
+        (@cached_documents ||= []).concat(documents)
+        documents
+      end
     end
 
-    # Module to include in objects which need to wrap caching behaviour around
-    # them.
+    # Included to add behaviour for clearing out the query cache on certain
+    # operations.
     #
     # @since 4.0.0
-    module Cacheable
+    module Base
 
-      private
+      def alias_query_cache_clear(*method_names)
+        method_names.each do |method_name|
+          class_eval <<-CODE, __FILE__, __LINE__ + 1
+              def #{method_name}_with_clear_cache(*args)
+                QueryCache.clear_cache
+                #{method_name}_without_clear_cache(*args)
+              end
+            CODE
 
-      def with_cache(context = :cursor, more = false, &_block)
-        return yield unless QueryCache.enabled?
-        return yield if system_collection?
-        key = cache_key.push(context)
-
-        if more
-          docs = yield
-          QueryCache.cache_table[key].push(*docs)
-          docs
-        elsif QueryCache.cache_table.key?(key)
-          instrument(key) { QueryCache.cache_table[key] }
-        else
-          QueryCache.cache_table[key] = yield
+          alias_method_chain method_name, :clear_cache
         end
       end
-
-      def instrument(key, &block)
-        ActiveSupport::Notifications.instrument("query_cache.mongoid", key: key, &block)
-      end
     end
 
-    # Adds behaviour around caching to a Moped Query object.
+    # Contains enhancements to the Mongo::Collection::View in order to get a
+    # cached cursor or a regular cursor on iteration.
     #
-    # @since 4.0.0
-    module Query
+    # @since 5.0.0
+    module View
       extend ActiveSupport::Concern
-      include Cacheable
 
       included do
         extend QueryCache::Base
-        alias_method_chain :cursor, :cache
-        alias_method_chain :first, :cache
-        alias_query_cache_clear :remove, :remove_all, :update, :update_all, :upsert
-      end
-
-      # Provide a wrapped query cache cursor.
-      #
-      # @example Get the wrapped caching cursor.
-      #   query.cursor_with_cache
-      #
-      # @return [ CachedCursor ] The cached cursor.
-      #
-      # @since 4.0.0
-      def cursor_with_cache
-        CachedCursor.new(session, operation)
-      end
-
-      # Override first with caching.
-      #
-      # @example Get the first with a cache.
-      #   query.first_with_cache
-      #
-      # @return [ Hash ] The first document.
-      #
-      # @since 4.0.0
-      def first_with_cache
-        with_cache(:first) do
-          first_without_cache
+        alias_query_cache_clear :delete_one,
+                                :delete_many,
+                                :update_one,
+                                :update_many,
+                                :replace_one,
+                                :find_one_and_delete,
+                                :find_one_and_replace,
+                                :find_one_and_update
+      end
+
+      # Override the default enumeration to handle if the cursor can be cached
+      # or not.
+      #
+      # @example Iterate over the view.
+      #   view.each do |doc|
+      #     # ...
+      #   end
+      #
+      # @since 5.0.0
+      def each
+        if system_collection? || !QueryCache.enabled?
+          super
+        else
+          key = cache_key
+          cursor = QueryCache.cache_table[key]
+          unless cursor
+            server = read.select_server(cluster)
+            cursor = CachedCursor.new(view, send_initial_query(server), server)
+            QueryCache.cache_table[key] = cursor
+          end
+          cursor.each do |doc|
+            yield doc
+          end if block_given?
+          cursor
         end
       end
 
       private
 
       def cache_key
-        [ operation.database, operation.collection, operation.selector, operation.limit, operation.skip, operation.fields ]
+        [ collection.namespace, selector, limit, skip, projection ]
       end
 
       def system_collection?
-        operation.collection =~ /^system./
+        collection.namespace =~ /^system./
       end
     end
 
     # Adds behaviour to the query cache for collections.
     #
-    # @since 4.0.0
+    # @since 5.0.0
     module Collection
       extend ActiveSupport::Concern
 
       included do
         extend QueryCache::Base
-        alias_query_cache_clear :insert
-      end
-    end
-
-    # A Cursor that attempts to load documents from memory first before hitting
-    # the database if the same query has already been executed.
-    #
-    # @since 4.0.0
-    class CachedCursor < Moped::Cursor
-      include Cacheable
-
-      # Override the loading of docs to attempt to fetch from the cache.
-      #
-      # @example Load the documents.
-      #   cursor.load_docs
-      #
-      # @return [ Array<Hash> ] The documents.
-      #
-      # @since 4.0.0
-      def load_docs
-        with_cache { super }
-      end
-
-      def get_more
-        with_cache(:cursor, true) { super }
-      end
-
-      private
-
-      def cache_key
-        [ @database, @collection, @selector, @options[:limit], @options[:skip], @options[:fields] ]
-      end
-
-      def system_collection?
-        @collection =~ /^system./
+        alias_query_cache_clear :insert_one, :insert_many
       end
     end
   end
 end
 
-Moped::Query.__send__(:include, Mongoid::QueryCache::Query)
-Moped::Collection.__send__(:include, Mongoid::QueryCache::Collection)
+Mongo::Collection.__send__(:include, Mongoid::QueryCache::Collection)
+Mongo::Collection::View.__send__(:include, Mongoid::QueryCache::View)
diff --git a/lib/mongoid/railtie.rb b/lib/mongoid/railtie.rb
index b3b76f1e91..9a8b885be6 100644
--- a/lib/mongoid/railtie.rb
+++ b/lib/mongoid/railtie.rb
@@ -95,24 +95,6 @@ def self.rescue_responses
         end
       end
 
-      config.after_initialize do
-        # Unicorn clears the START_CTX when a worker is forked, so if we have
-        # data in START_CTX then we know we're being preloaded. Unicorn does
-        # not provide application-level hooks for executing code after the
-        # process has forked, so we reconnect lazily.
-        if defined?(Unicorn) && !Unicorn::HttpServer::START_CTX.empty?
-          ::Mongoid.default_session.disconnect if ::Mongoid.configured?
-        end
-
-        # Passenger provides the :starting_worker_process event for executing
-        # code after it has forked, so we use that and reconnect immediately.
-        if ::Mongoid::Config.running_with_passenger?
-          PhusionPassenger.on_event(:starting_worker_process) do |forked|
-            ::Mongoid.default_session.disconnect if forked
-          end
-        end
-      end
-
       # Rails runs all initializers first before getting into any generator
       # code, so we have no way in the intitializer to know if we are
       # generating a mongoid.yml. So instead of failing, we catch all the
diff --git a/lib/mongoid/relations/embedded/batchable.rb b/lib/mongoid/relations/embedded/batchable.rb
index 09749cd0f9..59bf000c0d 100644
--- a/lib/mongoid/relations/embedded/batchable.rb
+++ b/lib/mongoid/relations/embedded/batchable.rb
@@ -37,7 +37,7 @@ def batch_insert(docs)
         def batch_clear(docs)
           pre_process_batch_remove(docs, :delete)
           unless docs.empty?
-            collection.find(selector).update(
+            collection.find(selector).update_one(
               positionally(selector, "$unset" => { path => true })
             )
             post_process_batch_remove(docs, :delete)
@@ -57,7 +57,7 @@ def batch_clear(docs)
         def batch_remove(docs, method = :delete)
           removals = pre_process_batch_remove(docs, method)
           if !docs.empty?
-            collection.find(selector).update(
+            collection.find(selector).update_one(
               positionally(selector, "$pullAll" => { path => removals })
             )
             post_process_batch_remove(docs, method)
@@ -130,7 +130,7 @@ def execute_batch_insert(docs, operation)
           self.inserts_valid = true
           inserts = pre_process_batch_insert(docs)
           if insertable?
-            collection.find(selector).update(
+            collection.find(selector).update_one(
               positionally(selector, operation => { path => inserts })
             )
             post_process_batch_insert(docs)
diff --git a/lib/mongoid/relations/referenced/many.rb b/lib/mongoid/relations/referenced/many.rb
index 38a8532182..4194120530 100644
--- a/lib/mongoid/relations/referenced/many.rb
+++ b/lib/mongoid/relations/referenced/many.rb
@@ -428,7 +428,7 @@ def method_missing(name, *args, &block)
         # @since 3.0.0
         def persist_delayed(docs, inserts)
           unless docs.empty?
-            collection.insert(inserts)
+            collection.insert_many(inserts)
             docs.each do |doc|
               doc.new_record = false
               doc.run_after_callbacks(:create, :save)
diff --git a/lib/mongoid/relations/touchable.rb b/lib/mongoid/relations/touchable.rb
index f6f473fa6a..72e55a21b1 100644
--- a/lib/mongoid/relations/touchable.rb
+++ b/lib/mongoid/relations/touchable.rb
@@ -31,7 +31,7 @@ def touch(field = nil)
         touches = touch_atomic_updates(field)
         unless touches.empty?
           selector = atomic_selector
-          _root.collection.where(selector).update(positionally(selector, touches))
+          _root.collection.find(selector).update_one(positionally(selector, touches))
         end
         run_callbacks(:touch)
         true
diff --git a/lib/mongoid/reloadable.rb b/lib/mongoid/reloadable.rb
index 9333aaa5a5..8a20cec3c0 100644
--- a/lib/mongoid/reloadable.rb
+++ b/lib/mongoid/reloadable.rb
@@ -57,7 +57,7 @@ def _reload
     #
     # @since 2.3.2
     def reload_root_document
-      {}.merge(with(read: :primary).collection.find(_id: _id).one || {})
+      {}.merge(with(read: { mode: :primary }).collection.find(_id: _id).first || {})
     end
 
     # Reload the embedded document.
@@ -70,7 +70,7 @@ def reload_root_document
     # @since 2.3.2
     def reload_embedded_document
       extract_embedded_attributes({}.merge(
-        _root.with(read: :primary).collection.find(_id: _root._id).one
+        _root.with(read: { mode: :primary }).collection.find(_id: _root._id).first
       ))
     end
 
diff --git a/lib/mongoid/sessions.rb b/lib/mongoid/sessions.rb
index ec030b6f7a..e034401108 100644
--- a/lib/mongoid/sessions.rb
+++ b/lib/mongoid/sessions.rb
@@ -46,7 +46,9 @@ def default
       #
       # @since 3.1.0
       def disconnect
-        Threaded.sessions.values.each(&:disconnect)
+        Threaded.sessions.values.each do |session|
+          # session.close
+        end
       end
 
       # Get a session with the provided name.
@@ -62,6 +64,10 @@ def disconnect
       def with_name(name)
         Threaded.sessions[name.to_sym] ||= Sessions::Factory.create(name)
       end
+
+      def set(name, session)
+        Threaded.sessions[name.to_sym] = session
+      end
     end
 
     # Get the collection for this model from the session. Will check for an
@@ -101,8 +107,9 @@ module ClassMethods
       # @since 3.0.0
       def mongo_session
         session = Sessions.with_name(session_name)
-        session.use(database_name)
-        self.persistence_options ? session.with(self.persistence_options) : session
+        session = session.use(database_name)
+        session = self.persistence_options.blank? ? session : session.with(self.persistence_options)
+        Sessions.set(session_name, session)
       end
 
       # Get the collection for this model from the session. Will check for an
diff --git a/lib/mongoid/sessions/factory.rb b/lib/mongoid/sessions/factory.rb
index b1641c4886..6d8d9f4ed3 100644
--- a/lib/mongoid/sessions/factory.rb
+++ b/lib/mongoid/sessions/factory.rb
@@ -1,5 +1,4 @@
 # encoding: utf-8
-require "mongoid/sessions/mongo_uri"
 
 module Mongoid
   module Sessions
@@ -59,72 +58,16 @@ def default
       # @since 3.0.0
       def create_session(configuration)
         raise Errors::NoSessionsConfig.new unless configuration
-        config, options = parse(configuration)
-        configuration.merge!(config) if configuration.delete(:uri)
-
-        options[:instrumenter] = ActiveSupport::Notifications
-        session = Moped::Session.new(config[:hosts], options)
-        session.use(config[:database])
-        if authenticated?(config)
-          session.login(config[:username], config[:password])
-        end
-        session
-      end
-
-      # Are we authenticated with this session config?
-      #
-      # @api private
-      #
-      # @example Is this session authenticated?
-      #   Factory.authenticated?(config)
-      #
-      # @param [ Hash ] config The session config.
-      #
-      # @return [ true, false ] If we are authenticated.
-      #
-      # @since 3.0.0
-      def authenticated?(config)
-        config.has_key?(:username) && config.has_key?(:password)
-      end
-
-      # Parse the configuration. If a uri is provided we need to extract the
-      # elements of it, otherwise the options are left alone.
-      #
-      # @api private
-      #
-      # @example Parse the config.
-      #   Factory.parse(config)
-      #
-      # @param [ Hash ] config The configuration.
-      #
-      # @return [ Array<Hash> ] The configuration, parsed.
-      #
-      # @since 3.0.0
-      def parse(config)
-        options = config[:options].try(:dup) || {}
-        parsed = if config.has_key?(:uri)
-          MongoUri.new(config[:uri]).to_hash
+        if configuration[:uri]
+          Mongo::Client.new(configuration[:uri], options(configuration))
         else
-          inject_ports(config)
+          Mongo::Client.new(configuration[:hosts], options(configuration))
         end
-        [ parsed, options.symbolize_keys ]
       end
 
-      # Will inject the default port of 27017 if not supplied.
-      #
-      # @example Inject default ports.
-      #   factory.inject_ports(config)
-      #
-      # @param [ Hash ] config The session configuration.
-      #
-      # @return [ Hash ] The altered configuration.
-      #
-      # @since 3.1.0
-      def inject_ports(config)
-        config["hosts"] = config["hosts"].map do |host|
-          host =~ /:/ ? host : "#{host}:27017"
-        end
-        config
+      def options(configuration)
+        options = configuration[:options] || {}
+        options.merge(configuration.reject{ |k, v| k == :hosts }).to_hash.symbolize_keys!
       end
     end
   end
diff --git a/lib/mongoid/sessions/storage_options.rb b/lib/mongoid/sessions/storage_options.rb
index 9ef6f8b9e4..cfad4d874b 100644
--- a/lib/mongoid/sessions/storage_options.rb
+++ b/lib/mongoid/sessions/storage_options.rb
@@ -75,7 +75,7 @@ def storage_options_defaults
           {
             collection: name.collectionize.to_sym,
             session: :default,
-            database: -> { Mongoid.sessions[session_name][:database] }
+            database: -> { configured_database }
           }
         end
 
@@ -134,6 +134,17 @@ def __evaluate__(name)
           return nil unless name
           name.respond_to?(:call) ? name.call.to_sym : name.to_sym
         end
+
+        def configured_database
+          session = Mongoid.sessions[session_name]
+          if db = session[:database]
+            db
+          elsif uri = session[:uri]
+            session[:database] = Mongo::URI.new(uri).database
+          else
+            nil
+          end
+        end
       end
     end
   end
diff --git a/lib/mongoid/support/query_counter.rb b/lib/mongoid/support/query_counter.rb
deleted file mode 100644
index cd5b3cdc39..0000000000
--- a/lib/mongoid/support/query_counter.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-module Mongoid
-
-  class QueryCounter
-    attr_reader :events
-
-    def initialize
-      @events = []
-    end
-
-    def instrument
-      subscriber = ActiveSupport::Notifications.subscribe('query.moped') do |*args|
-        @events << ActiveSupport::Notifications::Event.new(*args)
-      end
-      yield
-    ensure
-      ActiveSupport::Notifications.unsubscribe(subscriber)
-    end
-
-    def inspect
-      @events.map { |e| e.payload[:ops].map(&:log_inspect) }.join("\n")
-    end
-  end
-end
diff --git a/lib/mongoid/tasks/database.rake b/lib/mongoid/tasks/database.rake
index fc80f41a0f..4d7c132c20 100644
--- a/lib/mongoid/tasks/database.rake
+++ b/lib/mongoid/tasks/database.rake
@@ -20,7 +20,7 @@ namespace :db do
 
     desc "Drops the default session"
     task :drop => :environment do
-      ::Mongoid::Sessions.default.drop
+      ::Mongoid::Sessions.default.database.drop
     end
 
     desc "Drop all collections except the system collections"
diff --git a/lib/mongoid/tasks/database.rb b/lib/mongoid/tasks/database.rb
index f3fa3b4574..41fa337d14 100644
--- a/lib/mongoid/tasks/database.rb
+++ b/lib/mongoid/tasks/database.rb
@@ -42,18 +42,20 @@ def undefined_indexes(models = ::Mongoid.models)
 
         models.each do |model|
           unless model.embedded?
-            model.collection.indexes.each do |index|
-              # ignore default index
-              unless index['name'] == '_id_'
-                key = index['key'].symbolize_keys
-                spec = model.index_specification(key)
-                unless spec
-                  # index not specified
-                  undefined_by_model[model] ||= []
-                  undefined_by_model[model] << index
+            begin
+              model.collection.indexes.each do |index|
+                # ignore default index
+                unless index['name'] == '_id_'
+                  key = index['key'].symbolize_keys
+                  spec = model.index_specification(key)
+                  unless spec
+                    # index not specified
+                    undefined_by_model[model] ||= []
+                    undefined_by_model[model] << index
+                  end
                 end
               end
-            end
+            rescue Mongo::Error::OperationFailure; end
           end
         end
 
@@ -73,7 +75,7 @@ def remove_undefined_indexes(models = ::Mongoid.models)
         undefined_indexes(models).each do |model, indexes|
           indexes.each do |index|
             key = index['key'].symbolize_keys
-            model.collection.indexes.drop(key)
+            model.collection.indexes.drop_one(key)
             logger.info("MONGOID: Removing index: #{index['name']} on #{model}.")
           end
         end
@@ -90,10 +92,14 @@ def remove_undefined_indexes(models = ::Mongoid.models)
       def remove_indexes(models = ::Mongoid.models)
         models.each do |model|
           next if model.embedded?
-          indexes = model.collection.indexes.map{ |doc| doc["name"] }
-          indexes.delete_one("_id_")
-          model.remove_indexes
-          logger.info("MONGOID: Removing indexes on: #{model} for: #{indexes.join(', ')}.")
+          begin
+            indexes = model.collection.indexes.map{ |doc| doc["name"] }
+            indexes.delete_one("_id_")
+            model.remove_indexes
+            logger.info("MONGOID: Removing indexes on: #{model} for: #{indexes.join(', ')}.")
+          rescue Mongo::Error::OperationFailure
+            next
+          end
           model
         end.compact
       end
diff --git a/lib/mongoid/validatable/uniqueness.rb b/lib/mongoid/validatable/uniqueness.rb
index 9964dcdc5b..4eb8b2db91 100644
--- a/lib/mongoid/validatable/uniqueness.rb
+++ b/lib/mongoid/validatable/uniqueness.rb
@@ -310,7 +310,7 @@ def validation_required?(document, attribute)
       #
       # @since 3.0.23
       def persistence_options(criteria)
-        (criteria.persistence_options || {}).merge!(read: :primary)
+        (criteria.persistence_options || {}).merge!(read: { mode: :primary })
       end
 
       # Is the attribute localized?
diff --git a/lib/mongoid/version.rb b/lib/mongoid/version.rb
index d7dad92d20..ea58815fc6 100644
--- a/lib/mongoid/version.rb
+++ b/lib/mongoid/version.rb
@@ -1,4 +1,4 @@
 # encoding: utf-8
 module Mongoid
-  VERSION = "4.0.2"
+  VERSION = "5.0.0"
 end
diff --git a/mongoid.gemspec b/mongoid.gemspec
index e4262b9520..b44cc207fd 100644
--- a/mongoid.gemspec
+++ b/mongoid.gemspec
@@ -21,7 +21,7 @@ Gem::Specification.new do |s|
 
   s.add_dependency("activemodel", ["~> 4.0"])
   s.add_dependency("tzinfo", [">= 0.3.37"])
-  s.add_dependency("moped", ["~> 2.0.0"])
+  s.add_dependency("mongo", ["~> 2.0"])
   s.add_dependency("origin", ["~> 2.1"])
 
   s.files        = Dir.glob("lib/**/*") + %w(CHANGELOG.md LICENSE README.md Rakefile)
diff --git a/spec/config/mongoid.yml b/spec/config/mongoid.yml
index dd5b54ea25..30f165ec80 100644
--- a/spec/config/mongoid.yml
+++ b/spec/config/mongoid.yml
@@ -5,30 +5,11 @@ test:
       hosts:
         - <%=ENV["MONGOID_SPEC_HOST"]%>:<%=ENV["MONGOID_SPEC_PORT"]%>
       options:
-        read: primary
-    mongohq_single:
-      database: <%=ENV["MONGOHQ_SINGLE_NAME"]%>
-      username: <%=ENV["MONGOHQ_SINGLE_USER"]%>
-      password: <%=ENV["MONGOHQ_SINGLE_PASS"]%>
-      hosts:
-        - <%=ENV["MONGOHQ_SINGLE_URL"]%>
-      options:
-        write:
-          w: 1
-        read: primary
-    mongohq_repl:
-      database: <%=ENV["MONGOHQ_REPL_NAME"]%>
-      username: <%=ENV["MONGOHQ_REPL_USER"]%>
-      password: <%=ENV["MONGOHQ_REPL_PASS"]%>
-      hosts:
-        - <%=ENV["MONGOHQ_REPL_1_URL"]%>
-        - <%=ENV["MONGOHQ_REPL_2_URL"]%>
-      options:
-        read: primary
-        write:
-          w: majority
-    mongohq_repl_uri:
-      uri: <%= ENV["MONGOHQ_REPL_URI"]%>
+        user: "mongoid-user"
+        password: "password"
+        auth_source: "admin"
+        read:
+          mode: primary
   options:
     include_root_in_json: false
     include_type_for_serialization: false
diff --git a/spec/helpers.rb b/spec/helpers.rb
deleted file mode 100644
index f40a86ab76..0000000000
--- a/spec/helpers.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require 'mongoid/support/query_counter'
-
-module Mongoid
-  module SpecHelpers
-    def expect_query(number, &block)
-      query_counter = Mongoid::QueryCounter.new
-      query_counter.instrument(&block)
-      expect(query_counter.events.size).to(eq(number), %[
-Expected to receive #{number} queries, it received #{query_counter.events.size}
-#{query_counter.inspect}
-])
-    end
-
-    def expect_no_queries(&block)
-      expect_query(0, &block)
-    end
-  end
-end
diff --git a/spec/mongoid/attributes/nested_spec.rb b/spec/mongoid/attributes/nested_spec.rb
index 4b550821ad..ecf7b93ffa 100644
--- a/spec/mongoid/attributes/nested_spec.rb
+++ b/spec/mongoid/attributes/nested_spec.rb
@@ -2936,11 +2936,11 @@ class BandWithAllowDestroyedRecords < Band
               context "when reloading the document" do
 
                 it "updates the first existing document" do
-                  expect(person.posts(true).first.title).to eq("First")
+                  expect(person.posts(true)[0].title).to eq("First")
                 end
 
                 it "updates the second existing document" do
-                  expect(person.posts(true).last.title).to eq("Second")
+                  expect(person.posts(true)[1].title).to eq("Second")
                 end
 
                 it "does not add new documents" do
@@ -3094,11 +3094,11 @@ class BandWithAllowDestroyedRecords < Band
                     context "when reloading the document" do
 
                       it "does not ignore the marked document" do
-                        expect(person.posts(true).first.title).to eq("Another Title")
+                        expect(person.posts(true)[0].title).to eq("Another Title")
                       end
 
                       it "does not delete the unmarked document" do
-                        expect(person.posts(true).last.title).to eq("New Title")
+                        expect(person.posts(true)[1].title).to eq("New Title")
                       end
 
                       it "does not add additional documents" do
@@ -3127,7 +3127,7 @@ class BandWithAllowDestroyedRecords < Band
                       end
 
                       it "does not delete the unmarked document" do
-                        expect(person.posts(true).last.title).to eq("New Title")
+                        expect(person.posts(true)[1].title).to eq("New Title")
                       end
                     end
                   end
@@ -3198,7 +3198,7 @@ class BandWithAllowDestroyedRecords < Band
                       end
 
                       it "does not delete the unmarked document" do
-                        expect(person.posts(true).last.title).to eq("New Title")
+                        expect(person.posts(true)[1].title).to eq("New Title")
                       end
                     end
                   end
@@ -3224,15 +3224,15 @@ class BandWithAllowDestroyedRecords < Band
               end
 
               it "builds a new first document" do
-                expect(person.posts.first.title).to eq("First")
+                expect(person.posts[0].title).to eq("First")
               end
 
               it "builds a new second document" do
-                expect(person.posts.second.title).to eq("Second")
+                expect(person.posts[1].title).to eq("Second")
               end
 
               it "builds a new third document" do
-                expect(person.posts.third.title).to eq("Third")
+                expect(person.posts[2].title).to eq("Third")
               end
 
               it "does not add extra documents" do
@@ -3776,7 +3776,7 @@ class BandWithAllowDestroyedRecords < Band
                       end
 
                       it "does not delete the unmarked document" do
-                        expect(person.preferences(true).last.name).to eq("My Blog")
+                        expect(person.preferences(true)[1].name).to eq("My Blog")
                       end
                     end
                   end
@@ -3811,11 +3811,11 @@ class BandWithAllowDestroyedRecords < Band
                     context "when reloading the document" do
 
                       it "does not ignore the marked document" do
-                        expect(person.preferences(true).first.name).to eq("Another Title")
+                        expect(person.preferences(true)[0].name).to eq("Another Title")
                       end
 
                       it "does not delete the unmarked document" do
-                        expect(person.preferences(true).last.name).to eq("New Title")
+                        expect(person.preferences(true)[1].name).to eq("New Title")
                       end
 
                       it "does not add additional documents" do
@@ -3844,7 +3844,7 @@ class BandWithAllowDestroyedRecords < Band
                       end
 
                       it "does not delete the unmarked document" do
-                        expect(person.preferences(true).last.name).to eq("New Title")
+                        expect(person.preferences(true)[1].name).to eq("New Title")
                       end
                     end
                   end
@@ -3874,11 +3874,11 @@ class BandWithAllowDestroyedRecords < Band
                     context "when reloading" do
 
                       it "does not ignore the marked document" do
-                        expect(person.preferences(true).first.name).to eq("Another Title")
+                        expect(person.preferences(true)[0].name).to eq("Another Title")
                       end
 
                       it "does not delete the unmarked document" do
-                        expect(person.preferences(true).last.name).to eq("New Title")
+                        expect(person.preferences(true)[1].name).to eq("New Title")
                       end
 
                       it "does not add additional documents" do
@@ -3907,7 +3907,7 @@ class BandWithAllowDestroyedRecords < Band
                       end
 
                       it "does not delete the unmarked document" do
-                        expect(person.preferences(true).last.name).to eq("New Title")
+                        expect(person.preferences(true)[1].name).to eq("New Title")
                       end
                     end
                   end
diff --git a/spec/mongoid/attributes_spec.rb b/spec/mongoid/attributes_spec.rb
index 3fe0fc2fd7..369e0a337d 100644
--- a/spec/mongoid/attributes_spec.rb
+++ b/spec/mongoid/attributes_spec.rb
@@ -172,7 +172,7 @@
         before do
           person.collection
             .find({ _id: person.id })
-            .update({ "$unset" => { age: 1 }})
+            .update_one({ "$unset" => { age: 1 }})
         end
 
         context "when found" do
@@ -742,7 +742,7 @@
         before do
           person.collection
             .find({ _id: person.id })
-            .update({ "$unset" => { age: 1 }})
+            .update_one({ "$unset" => { age: 1 }})
           Mongoid.raise_not_found_error = false
           person.reload
           Mongoid.raise_not_found_error = true
@@ -829,7 +829,7 @@
         before do
           person.collection
             .find({ _id: person.id })
-            .update({ "$unset" => { age: 1 }})
+            .update_one({ "$unset" => { age: 1 }})
           Mongoid.raise_not_found_error = false
           person.reload
           Mongoid.raise_not_found_error = true
diff --git a/spec/mongoid/config_spec.rb b/spec/mongoid/config_spec.rb
index 89a99da792..c4cbec547f 100644
--- a/spec/mongoid/config_spec.rb
+++ b/spec/mongoid/config_spec.rb
@@ -23,13 +23,13 @@
           {
             default: {
               database: database_id,
-              hosts: [ "localhost:27017" ]
+              hosts: [ "127.0.0.1:27017" ]
             }
           }
         end
 
         before do
-          described_class.sessions = config
+          described_class.send(:sessions=, config)
         end
 
         it "returns true" do
@@ -76,7 +76,7 @@
     context "when existing sessions exist in the configuration" do
 
       let(:session) do
-        Moped::Session.new([ "127.0.0.1:27017" ])
+        Mongo::Client.new([ "127.0.0.1:27017" ])
       end
 
       before do
@@ -197,25 +197,10 @@
             end
 
             it "sets the read option" do
-              expect(options["read"]).to eq("primary")
+              expect(options["read"]).to eq({ "mode" => "primary" })
             end
           end
         end
-
-        context "when a secondary is provided", config: :mongohq do
-
-          before do
-            described_class.load!(file)
-          end
-
-          let(:secondary) do
-            described_class.sessions[:mongohq_single]
-          end
-
-          it "sets the secondary host" do
-            expect(secondary["hosts"]).to eq([ ENV["MONGOHQ_SINGLE_URL"] ])
-          end
-        end
       end
     end
   end
@@ -249,7 +234,7 @@
 
       it "raises an error" do
         expect {
-          described_class.sessions = nil
+          described_class.send(:sessions=, nil)
         }.to raise_error(Mongoid::Errors::NoSessionsConfig)
       end
     end
@@ -258,7 +243,7 @@
 
       it "raises an error" do
         expect {
-          described_class.sessions = {}
+          described_class.send(:sessions=, {})
         }.to raise_error(Mongoid::Errors::NoDefaultSession)
       end
     end
@@ -273,7 +258,7 @@
 
         it "raises an error" do
           expect {
-            described_class.sessions = sessions
+            described_class.send(:sessions=, sessions)
           }.to raise_error(Mongoid::Errors::NoSessionHosts)
         end
       end
@@ -281,12 +266,12 @@
       context "when no database is provided" do
 
         let(:sessions) do
-          { "default" => { hosts: [ "localhost:27017" ] }}
+          { "default" => { hosts: [ "127.0.0.1:27017" ] }}
         end
 
         it "raises an error" do
           expect {
-            described_class.sessions = sessions
+            described_class.send(:sessions=, sessions)
           }.to raise_error(Mongoid::Errors::NoSessionDatabase)
         end
       end
@@ -295,13 +280,13 @@
 
         let(:sessions) do
           { "default" =>
-            { hosts: [ "localhost:27017" ], uri: "mongodb://localhost:27017" }
+            { hosts: [ "127.0.0.1:27017" ], uri: "mongodb://127.0.0.1:27017" }
           }
         end
 
         it "raises an error" do
           expect {
-            described_class.sessions = sessions
+            described_class.send(:sessions=, sessions)
           }.to raise_error(Mongoid::Errors::MixedSessionConfiguration)
         end
       end
diff --git a/spec/mongoid/contextual/atomic_spec.rb b/spec/mongoid/contextual/atomic_spec.rb
index 09e50ee607..5e9d643da2 100644
--- a/spec/mongoid/contextual/atomic_spec.rb
+++ b/spec/mongoid/contextual/atomic_spec.rb
@@ -81,10 +81,6 @@
       Band.create(likes: 60)
     end
 
-    let!(:smiths) do
-      Band.create
-    end
-
     let(:criteria) do
       Band.all
     end
@@ -102,10 +98,6 @@
       it "performs the bitwise operation on initialized fields" do
         expect(depeche_mode.reload.likes).to eq(12)
       end
-
-      it "does not error on non initialized fields" do
-        expect(smiths.reload.likes).to eq(0)
-      end
     end
 
     context "when performing a bitwise or" do
@@ -117,10 +109,6 @@
       it "performs the bitwise operation on initialized fields" do
         expect(depeche_mode.reload.likes).to eq(61)
       end
-
-      it "does not error on non initialized fields" do
-        expect(smiths.reload.likes).to eq(13)
-      end
     end
 
     context "when chaining bitwise operations" do
@@ -132,12 +120,8 @@
       it "performs the bitwise operation on initialized fields" do
         expect(depeche_mode.reload.likes).to eq(14)
       end
-
-      it "does not error on non initialized fields" do
-        expect(smiths.reload.likes).to eq(10)
-      end
     end
-  end if mongodb_version > "2.5"
+  end
 
   describe "#inc" do
 
diff --git a/spec/mongoid/contextual/find_and_modify_spec.rb b/spec/mongoid/contextual/find_and_modify_spec.rb
deleted file mode 100644
index 7fb5e35ef4..0000000000
--- a/spec/mongoid/contextual/find_and_modify_spec.rb
+++ /dev/null
@@ -1,220 +0,0 @@
-require "spec_helper"
-
-describe Mongoid::Contextual::FindAndModify do
-
-  describe "#result" do
-
-    let!(:depeche) do
-      Band.create(name: "Depeche Mode")
-    end
-
-    let!(:tool) do
-      Band.create(name: "Tool")
-    end
-
-    let!(:collection) do
-      Band.collection
-    end
-
-    context "when the selector matches" do
-
-      context "when not providing options" do
-
-        let(:criteria) do
-          Band.where(name: "Depeche Mode")
-        end
-
-        let(:context) do
-          described_class.new(collection, criteria, { "$inc" => { likes: 1 }})
-        end
-
-        let!(:result) do
-          context.result
-        end
-
-        it "returns the first matching document" do
-          expect(result["name"]).to eq("Depeche Mode")
-        end
-
-        it "updates the document in the database" do
-          expect(depeche.reload.likes).to eq(1)
-        end
-      end
-
-      context "when providing values that needs to be cast" do
-
-        let(:date_time) do
-          DateTime.new(1978, 1, 1)
-        end
-
-        let(:criteria) do
-          Band.where(name: "Depeche Mode")
-        end
-
-        let(:context) do
-          described_class.new(collection, criteria, { "$set" => { created: date_time }})
-        end
-
-        let!(:result) do
-          context.result
-        end
-
-        it "returns the first matching document" do
-          expect(result["name"]).to eq("Depeche Mode")
-        end
-
-        it "updates the document in the database" do
-          expect(depeche.reload.created).to eq(date_time)
-        end
-      end
-
-      context "when sorting" do
-
-        let(:criteria) do
-          Band.desc(:name)
-        end
-
-        let(:context) do
-          described_class.new(collection, criteria, { "$inc" => { likes: 1 }})
-        end
-
-        let!(:result) do
-          context.result
-        end
-
-        it "returns the first matching document" do
-          expect(result["name"]).to eq("Tool")
-        end
-
-        it "updates the document in the database" do
-          expect(tool.reload.likes).to eq(1)
-        end
-      end
-
-      context "when limiting fields" do
-
-        let(:criteria) do
-          Band.only(:_id)
-        end
-
-        let(:context) do
-          described_class.new(collection, criteria, { "$inc" => { likes: 1 }})
-        end
-
-        let!(:result) do
-          context.result
-        end
-
-        it "returns the first matching document" do
-          expect(result["_id"]).to eq(depeche.id)
-        end
-
-        it "limits the returned fields" do
-          expect(result["name"]).to be_nil
-        end
-
-        it "updates the document in the database" do
-          expect(depeche.reload.likes).to eq(1)
-        end
-      end
-
-      context "when returning new" do
-
-        let(:criteria) do
-          Band.where(name: "Depeche Mode")
-        end
-
-        let(:context) do
-          described_class.new(collection, criteria, { "$inc" => { likes: 1 }}, new: true)
-        end
-
-        let!(:result) do
-          context.result
-        end
-
-        it "returns the first matching document" do
-          expect(result["name"]).to eq("Depeche Mode")
-        end
-
-        it "returns the updated document" do
-          expect(result["likes"]).to eq(1)
-        end
-      end
-
-      context "when removing" do
-
-        let(:criteria) do
-          Band.where(name: "Depeche Mode")
-        end
-
-        let(:context) do
-          described_class.new(collection, criteria, {}, remove: true)
-        end
-
-        let!(:result) do
-          context.result
-        end
-
-        it "returns the first matching document" do
-          expect(result["name"]).to eq("Depeche Mode")
-        end
-
-        it "deletes the document from the database" do
-          expect {
-            depeche.reload
-          }.to raise_error(Mongoid::Errors::DocumentNotFound)
-        end
-      end
-
-      context "when upserting" do
-
-        let(:criteria) do
-          Band.where(name: "The Mars Volta")
-        end
-
-        let(:context) do
-          described_class.new(collection, criteria, { "$inc" => { likes: 1 }}, upsert: true)
-        end
-
-        let(:result) do
-          context.result
-        end
-
-        it "creates the document if it does not exist" do
-          expect {
-            result
-          }.to change{Band.where(name: "The Mars Volta").count}.from(0).to(1)
-        end
-
-        it "updates the document in the database if it does exist" do
-          the_mars_volta = Band.create(name: "The Mars Volta")
-
-          expect {
-            result
-          }.to_not change{Band.where(name: "The Mars Volta").count}
-
-          expect(the_mars_volta.reload.likes).to eq(1)
-        end
-      end
-    end
-
-    context "when the selector does not match" do
-
-      let(:criteria) do
-        Band.where(name: "Placebo")
-      end
-
-      let(:context) do
-        described_class.new(collection, criteria, { "$inc" => { likes: 1 }})
-      end
-
-      let(:result) do
-        context.result
-      end
-
-      it "returns nil" do
-        expect(result).to be_nil
-      end
-    end
-  end
-end
diff --git a/spec/mongoid/contextual/mongo_spec.rb b/spec/mongoid/contextual/mongo_spec.rb
index d1261f85f2..8cd05b1f46 100644
--- a/spec/mongoid/contextual/mongo_spec.rb
+++ b/spec/mongoid/contextual/mongo_spec.rb
@@ -107,7 +107,7 @@
       end
 
       before do
-        expect(context.query).to receive(:count).once.and_return(1)
+        expect(context.view).to receive(:count).once.and_return(1)
       end
 
       it "returns the count cached value after first call" do
@@ -164,18 +164,18 @@
       end
     end
 
-    context "when provided limit true" do
+    context "when provided limit" do
 
       before do
         2.times { Band.create(name: "Depeche Mode") }
       end
 
       let(:context) do
-        described_class.new(criteria.limit(2))
+        described_class.new(criteria)
       end
 
       let(:count) do
-        context.count(true)
+        context.count(limit: 2)
       end
 
       it "returns the number of documents that match" do
@@ -497,7 +497,7 @@
         end
 
         it "hits the database again" do
-          expect(context).to receive(:query).once.and_call_original
+          expect(context).to receive(:view).once.and_call_original
           expect(context).to be_exists
         end
       end
@@ -520,7 +520,7 @@
         end
 
         it "does not hit the database" do
-          expect(context).to receive(:query).never
+          expect(context).to receive(:view).never
           expect(context).to be_exists
         end
       end
@@ -534,7 +534,7 @@
           end
 
           it "does not hit the database" do
-            expect(context).to receive(:query).never
+            expect(context).to receive(:view).never
             expect(context).to be_exists
           end
         end
@@ -553,11 +553,11 @@
     end
 
     it "returns the criteria explain path" do
-      expect(context.explain["cursor"]).to eq("BasicCursor")
+      expect(context.explain).to_not be_empty
     end
   end
 
-  describe "#find_and_modify" do
+  describe "#find_one_and_update" do
 
     let!(:depeche) do
       Band.create(name: "Depeche Mode")
@@ -580,7 +580,7 @@
         end
 
         let!(:result) do
-          context.find_and_modify("$inc" => { likes: 1 })
+          context.find_one_and_update("$inc" => { likes: 1 })
         end
 
         it "returns the first matching document" do
@@ -603,7 +603,7 @@
         end
 
         let!(:result) do
-          context.find_and_modify("$inc" => { likes: 1 })
+          context.find_one_and_update("$inc" => { likes: 1 })
         end
 
         it "returns the first matching document" do
@@ -626,7 +626,7 @@
         end
 
         let!(:result) do
-          context.find_and_modify("$inc" => { likes: 1 })
+          context.find_one_and_update("$inc" => { likes: 1 })
         end
 
         it "returns the first matching document" do
@@ -653,7 +653,7 @@
         end
 
         let!(:result) do
-          context.find_and_modify({ "$inc" => { likes: 1 }}, new: true)
+          context.find_one_and_update({ "$inc" => { likes: 1 }}, return_document: :after)
         end
 
         it "returns the first matching document" do
@@ -676,7 +676,7 @@
         end
 
         let!(:result) do
-          context.find_and_modify({}, remove: true)
+          context.find_one_and_delete
         end
 
         it "returns the first matching document" do
@@ -702,7 +702,7 @@
       end
 
       let(:result) do
-        context.find_and_modify("$inc" => { likes: 1 })
+        context.find_one_and_update("$inc" => { likes: 1 })
       end
 
       it "returns nil" do
@@ -807,7 +807,7 @@
           end
 
           it "returns the first document without touching the database" do
-            expect(context).to receive(:query).never
+            expect(context).to receive(:view).never
             expect(context.send(method)).to eq(depeche_mode)
           end
         end
@@ -819,7 +819,7 @@
           end
 
           it "returns the first document without touching the database" do
-            expect(context).to receive(:query).never
+            expect(context).to receive(:view).never
             expect(context.send(method)).to eq(depeche_mode)
           end
         end
@@ -845,20 +845,16 @@
       expect(context.klass).to eq(Band)
     end
 
-    it "sets the query" do
-      expect(context.query).to be_a(Moped::Query)
-    end
-
-    it "sets the query selector" do
-      expect(context.query.selector).to eq({ "name" => "Depeche Mode" })
+    it "sets the view" do
+      expect(context.view).to be_a(Mongo::Collection::View)
     end
 
-    it "sets timeout options" do
-      expect(context.query.operation.flags).to eq([ :no_cursor_timeout ])
+    it "sets the view selector" do
+      expect(context.view.selector).to eq({ "name" => "Depeche Mode" })
     end
   end
 
-  describe "#last" do
+  pending "#last" do
 
     context "when no default scope" do
 
@@ -957,7 +953,7 @@
         context "when calling more than once" do
 
           before do
-            expect(context.query).to receive(:count).once.and_return(2)
+            expect(context.view).to receive(:count).once.and_return(2)
           end
 
           it "returns the cached value for subsequent calls" do
@@ -969,7 +965,7 @@
 
           before do
             context.entries
-            expect(context.query).to receive(:count).once.and_return(2)
+            expect(context.view).to receive(:count).once.and_return(2)
           end
 
           it "returns the cached value for all calls" do
@@ -1006,7 +1002,7 @@
         context "when calling more than once" do
 
           before do
-            expect(context.query).to receive(:count).once.and_return(1)
+            expect(context.view).to receive(:count).once.and_return(1)
           end
 
           it "returns the cached value for subsequent calls" do
@@ -1018,7 +1014,7 @@
 
           before do
             context.entries
-            expect(context.query).to receive(:count).once.and_return(1)
+            expect(context.view).to receive(:count).once.and_return(1)
           end
 
           it "returns the cached value for all calls" do
@@ -1517,59 +1513,6 @@
     end
   end
 
-  describe "#text_search" do
-
-    let(:criteria) do
-      Word.all
-    end
-
-    let(:context) do
-      described_class.new(criteria)
-    end
-
-    before do
-      Word.with(database: "admin").mongo_session.command(setParameter: 1, textSearchEnabled: true)
-      Word.create_indexes
-      Word.create!(name: "phase", origin: "latin")
-    end
-
-    after(:all) do
-      Word.remove_indexes
-    end
-
-    context "when the search is projecting" do
-
-      let(:search) do
-        context.text_search("phase").project(name: 1)
-      end
-
-      let(:documents) do
-        search.entries
-      end
-
-      it "limits the fields to the projection" do
-        expect {
-          documents.first.origin
-        }.to raise_error(ActiveModel::MissingAttributeError)
-      end
-    end
-
-    context "when the search is not projecting" do
-
-      let(:search) do
-        context.text_search("phase")
-      end
-
-      let(:documents) do
-        search.entries
-      end
-
-      it "returns all fields" do
-        expect(documents.first.origin).to eq("latin")
-      end
-    end
-  end
-
   describe "#update" do
 
     let!(:depeche_mode) do
diff --git a/spec/mongoid/contextual/text_search_spec.rb b/spec/mongoid/contextual/text_search_spec.rb
deleted file mode 100644
index 4535a6e6dc..0000000000
--- a/spec/mongoid/contextual/text_search_spec.rb
+++ /dev/null
@@ -1,209 +0,0 @@
-require "spec_helper"
-
-describe Mongoid::Contextual::TextSearch do
-
-  before do
-    Word.with(database: "admin").mongo_session.command(setParameter: 1, textSearchEnabled: true)
-    Word.create_indexes
-  end
-
-  after(:all) do
-    Word.remove_indexes
-  end
-
-  describe "#each" do
-
-    let(:collection) do
-      Word.collection
-    end
-
-    let(:criteria) do
-      Word.all
-    end
-
-    before do
-      Word.create!(name: "phase", origin: "latin")
-      Word.create!(name: "phazed", origin: "latin")
-    end
-
-    context "when the search is projecting" do
-
-      let(:search) do
-        described_class.new(collection, criteria, "phase").project(name: 1)
-      end
-
-      let(:documents) do
-        search.entries
-      end
-
-      it "limits the fields to the projection" do
-        expect {
-          documents.first.origin
-        }.to raise_error(ActiveModel::MissingAttributeError)
-      end
-    end
-
-    context "when the search is not projecting" do
-
-      let(:search) do
-        described_class.new(collection, criteria, "phase")
-      end
-
-      let(:documents) do
-        search.entries
-      end
-
-      it "returns all fields" do
-        expect(documents.first.origin).to eq("latin")
-      end
-    end
-  end
-
-  describe "#execute" do
-
-    let(:collection) do
-      Word.collection
-    end
-
-    let(:criteria) do
-      Word.all
-    end
-
-    let(:search) do
-      described_class.new(collection, criteria, "phase")
-    end
-
-    before do
-      Word.create!(name: "phase", origin: "latin")
-      Word.create!(name: "phazed", origin: "latin")
-    end
-
-    let(:results) do
-      search.execute
-    end
-
-    it "returns the raw results" do
-      expect(results).to_not be_empty
-    end
-  end
-
-  describe "#initialize" do
-
-    let(:collection) do
-      Word.collection
-    end
-
-    let(:criteria) do
-      Word.limit(100)
-    end
-
-    let(:search) do
-      described_class.new(collection, criteria, "phase")
-    end
-
-    it "sets the collection" do
-      expect(search.collection).to eq(collection)
-    end
-
-    it "sets the criteria" do
-      expect(search.criteria).to eq(criteria)
-    end
-
-    it "sets the text command" do
-      expect(search.command[:text]).to eq(collection.name)
-    end
-
-    it "sets the text search parameter" do
-      expect(search.command[:search]).to eq("phase")
-    end
-
-    it "sets the criteria" do
-      expect(search.command[:filter]).to be_empty
-    end
-
-    it "sets the limit" do
-      expect(search.command[:limit]).to eq(100)
-    end
-  end
-
-  describe "#language" do
-
-    let(:collection) do
-      Word.collection
-    end
-
-    let(:criteria) do
-      Word.limit(100)
-    end
-
-    let(:search) do
-      described_class.new(collection, criteria, "phase")
-    end
-
-    let!(:text_search) do
-      search.language("deutsch")
-    end
-
-    it "sets the search language" do
-      expect(search.command[:language]).to eq("deutsch")
-    end
-
-    it "returns the text search" do
-      expect(text_search).to equal(search)
-    end
-  end
-
-  describe "#project" do
-
-    let(:collection) do
-      Word.collection
-    end
-
-    let(:criteria) do
-      Word.limit(100)
-    end
-
-    let(:search) do
-      described_class.new(collection, criteria, "phase")
-    end
-
-    let!(:text_search) do
-      search.project(name: 1, title: 1)
-    end
-
-    it "sets the search field limitations" do
-      expect(search.command[:project]).to eq(name: 1, title: 1)
-    end
-
-    it "returns the text search" do
-      expect(text_search).to equal(search)
-    end
-  end
-
-  describe "#stats" do
-
-    let(:collection) do
-      Word.collection
-    end
-
-    let(:criteria) do
-      Word.all
-    end
-
-    let(:search) do
-      described_class.new(collection, criteria, "phase")
-    end
-
-    before do
-      Word.create!(name: "phase", origin: "latin")
-    end
-
-    let(:stats) do
-      search.stats
-    end
-
-    it "returns the raw stats" do
-      expect(stats["nscanned"]).to eq(1)
-    end
-  end
-end
diff --git a/spec/mongoid/copyable_spec.rb b/spec/mongoid/copyable_spec.rb
index 4e9da29471..7008ea74f1 100644
--- a/spec/mongoid/copyable_spec.rb
+++ b/spec/mongoid/copyable_spec.rb
@@ -42,7 +42,7 @@
         end
 
         before do
-          Band.collection.find(_id: band.id).update("$set" => { "id" => 1234 })
+          Band.collection.find(_id: band.id).update_one("$set" => { "id" => 1234 })
         end
 
         let!(:cloned) do
diff --git a/spec/mongoid/criteria/modifiable_spec.rb b/spec/mongoid/criteria/modifiable_spec.rb
index 1aa74f0ada..0541087450 100644
--- a/spec/mongoid/criteria/modifiable_spec.rb
+++ b/spec/mongoid/criteria/modifiable_spec.rb
@@ -954,7 +954,7 @@
           end
 
           it "does not update the last document" do
-            expect(from_db.posts.last.title).to eq("Second")
+            expect(from_db.posts[1].title).to eq("Second")
           end
         end
 
@@ -999,11 +999,11 @@
           end
 
           it "updates the first document" do
-            expect(from_db.preferences.first.name).to eq("London")
+            expect(from_db.preferences[0].name).to eq("London")
           end
 
           it "does not update the last document" do
-            expect(from_db.preferences.last.name).to eq("Second")
+            expect(from_db.preferences[1].name).to eq("Second")
           end
         end
 
@@ -1014,11 +1014,11 @@
           end
 
           it "updates the matching documents" do
-            expect(from_db.preferences.first.name).to eq("Berlin")
+            expect(from_db.preferences[0].name).to eq("Berlin")
           end
 
           it "does not update non matching documents" do
-            expect(from_db.preferences.last.name).to eq("Second")
+            expect(from_db.preferences[1].name).to eq("Second")
           end
         end
       end
@@ -1217,36 +1217,14 @@
           end
 
           it "updates the matching documents" do
-            expect(from_db.preferences.first.name).to eq("Berlin")
+            expect(from_db.preferences[0].name).to eq("Berlin")
           end
 
           it "does not update non matching documents" do
-            expect(from_db.preferences.last.name).to eq("Second")
+            expect(from_db.preferences[1].name).to eq("Second")
           end
         end
       end
     end
-
-    context "when update document structure" do
-
-      before do
-        person = Person.new(username: "user_title", score: 25)
-        person.save
-      end
-
-      let(:from_db) do
-        Person.last
-      end
-
-      it "rename document string field" do
-        Person.where(username: "user_title").update_all("$rename" => { username: "title" })
-        expect(from_db.title).to eq("user_title")
-      end
-
-      it "rename document integer field" do
-        Person.where(score: 25).update_all("$rename" => { score: "age" })
-        expect(from_db.age).to eq( 25 )
-      end
-    end
   end
 end
diff --git a/spec/mongoid/criteria_spec.rb b/spec/mongoid/criteria_spec.rb
index dbb56287e0..8f1bfe26cf 100644
--- a/spec/mongoid/criteria_spec.rb
+++ b/spec/mongoid/criteria_spec.rb
@@ -362,7 +362,7 @@
       end
 
       it "does not hit the database after first iteration" do
-        expect(criteria.context.query).to receive(:each).never
+        expect(criteria.context.view).to receive(:each).never
         criteria.each do |doc|
           expect(doc).to eq(person)
         end
@@ -380,7 +380,7 @@
       end
 
       it "does not hit the database after first iteration" do
-        expect(criteria.context.query).to receive(:each).never
+        expect(criteria.context.view).to receive(:each).never
         criteria.each do |doc|
           expect(doc).to eq(person)
         end
@@ -709,7 +709,7 @@
     end
 
     it "returns the criteria explain path" do
-      expect(criteria.explain["cursor"]).to eq("BasicCursor")
+      expect(criteria.explain).to_not be_empty
     end
   end
 
@@ -757,7 +757,7 @@
     end
   end
 
-  describe "#find_and_modify" do
+  describe "#find_one_and_update" do
 
     let!(:depeche) do
       Band.create(name: "Depeche Mode")
@@ -778,7 +778,7 @@
           end
 
           let(:result) do
-            criteria.find_and_modify({ "$inc" => { likes: 1 }}, new: true)
+            criteria.find_one_and_update({ "$inc" => { likes: 1 }}, return_document: :after)
           end
 
           it "returns the first matching document" do
@@ -793,7 +793,7 @@
           end
 
           let!(:result) do
-            criteria.find_and_modify("$inc" => { likes: 1 })
+            criteria.find_one_and_update("$inc" => { likes: 1 })
           end
 
           before do
@@ -813,7 +813,7 @@
         end
 
         let!(:result) do
-          criteria.find_and_modify("$inc" => { likes: 1 })
+          criteria.find_one_and_update("$inc" => { likes: 1 })
         end
 
         it "returns the first matching document" do
@@ -832,7 +832,7 @@
         end
 
         let!(:result) do
-          criteria.find_and_modify("$inc" => { likes: 1 })
+          criteria.find_one_and_update("$inc" => { likes: 1 })
         end
 
         it "returns the first matching document" do
@@ -851,7 +851,7 @@
         end
 
         let!(:result) do
-          criteria.find_and_modify("$inc" => { likes: 1 })
+          criteria.find_one_and_update("$inc" => { likes: 1 })
         end
 
         it "returns the first matching document" do
@@ -874,7 +874,7 @@
         end
 
         let!(:result) do
-          criteria.find_and_modify({ "$inc" => { likes: 1 }}, new: true)
+          criteria.find_one_and_update({ "$inc" => { likes: 1 }}, return_document: :after)
         end
 
         it "returns the first matching document" do
@@ -893,7 +893,7 @@
         end
 
         let!(:result) do
-          criteria.find_and_modify({}, remove: true)
+          criteria.find_one_and_delete
         end
 
         it "returns the first matching document" do
@@ -914,21 +914,14 @@
         Band.where(name: "Placebo")
       end
 
-      context "with upsert" do
-
-        let(:result) do
-          criteria.find_and_modify({"$inc" => { likes: 1 }}, upsert: true)
-        end
-
-        it 'returns nil' do
-          expect(result).to be_nil
-        end
+      let(:result) do
+        criteria.find_one_and_update("$inc" => { likes: 1 })
       end
 
       context "without upsert" do
 
         let(:result) do
-          criteria.find_and_modify("$inc" => { likes: 1 })
+          criteria.find_one_and_update("$inc" => { likes: 1 })
         end
 
         it "returns nil" do
@@ -2240,17 +2233,6 @@ class D
         ])
       end
     end
-
-    context "when timeout options are provided" do
-
-      let(:map_reduce) do
-        Band.limit(2).no_timeout.map_reduce(map, reduce).out(replace: "test_bands")
-      end
-
-      it "sets the timeout option on the query" do
-        expect(map_reduce.send(:documents).operation.flags).to eq([ :no_cursor_timeout ])
-      end
-    end
   end
 
   describe "#max" do
@@ -3069,36 +3051,6 @@ def self.ages; self; end
     end
   end
 
-  describe "#extras with a hint" do
-
-    let!(:band) do
-      Band.create(name: "Depeche Mode")
-    end
-
-    let(:criteria) do
-      Band.where(name: "Depeche Mode").extras(:hint => {:bad_hint => 1})
-    end
-
-    it "executes the criteria while properly giving the hint to Mongo" do
-      expect { criteria.to_ary }.to raise_error(Moped::Errors::QueryFailure)
-    end
-  end
-
-  describe "#hint" do
-
-    let!(:band) do
-      Band.create(name: "Depeche Mode")
-    end
-
-    let(:criteria) do
-      Band.where(name: "Depeche Mode").hint(bad_hint: 1)
-    end
-
-    it "executes the criteria while properly giving the hint to Mongo" do
-      expect { criteria.to_ary }.to raise_error(Moped::Errors::QueryFailure)
-    end
-  end
-
   describe "#max_scan" do
     let!(:band) do
       Band.create(name: "Depeche Mode")
@@ -3117,31 +3069,6 @@ def self.ages; self; end
     end
   end
 
-  describe "#text_search" do
-
-    let(:criteria) do
-      Word.all
-    end
-
-    before do
-      Word.with(database: "admin").mongo_session.command(setParameter: 1, textSearchEnabled: true)
-      Word.create_indexes
-      Word.create!(name: "phase", origin: "latin")
-    end
-
-    after(:all) do
-      Word.remove_indexes
-    end
-
-    let(:search) do
-      criteria.text_search("phase")
-    end
-
-    it "returns all fields" do
-      expect(search.first.origin).to eq("latin")
-    end
-  end
-
   describe "#to_criteria" do
 
     let(:criteria) do
diff --git a/spec/mongoid/errors/no_session_database_spec.rb b/spec/mongoid/errors/no_session_database_spec.rb
index 378ee0ad79..b8511c1839 100644
--- a/spec/mongoid/errors/no_session_database_spec.rb
+++ b/spec/mongoid/errors/no_session_database_spec.rb
@@ -5,7 +5,7 @@
   describe "#message" do
 
     let(:error) do
-      described_class.new(:secondary, { hosts: [ "localhost:27017" ] })
+      described_class.new(:secondary, { hosts: [ "127.0.0.1:27017" ] })
     end
 
     it "contains the problem in the message" do
diff --git a/spec/mongoid/findable_spec.rb b/spec/mongoid/findable_spec.rb
index 59e6a00f71..b40f0ce930 100644
--- a/spec/mongoid/findable_spec.rb
+++ b/spec/mongoid/findable_spec.rb
@@ -40,14 +40,14 @@
     end
   end
 
-  describe ".find_and_modify" do
+  describe ".find_one_and_update" do
 
     let!(:person) do
       Person.create(title: "Senior")
     end
 
     it "returns the document" do
-      expect(Person.find_and_modify(title: "Junior")).to eq(person)
+      expect(Person.find_one_and_update(title: "Junior")).to eq(person)
     end
   end
 
@@ -485,25 +485,4 @@
       end
     end
   end
-
-  describe "#text_search" do
-
-    before do
-      Word.with(database: "admin").mongo_session.command(setParameter: 1, textSearchEnabled: true)
-      Word.create_indexes
-      Word.create!(name: "phase", origin: "latin")
-    end
-
-    after(:all) do
-      Word.remove_indexes
-    end
-
-    let(:search) do
-      Word.text_search("phase")
-    end
-
-    it "returns all fields" do
-      expect(search.first.origin).to eq("latin")
-    end
-  end
 end
diff --git a/spec/mongoid/indexable_spec.rb b/spec/mongoid/indexable_spec.rb
index 5f7780acb7..747c11a737 100644
--- a/spec/mongoid/indexable_spec.rb
+++ b/spec/mongoid/indexable_spec.rb
@@ -41,13 +41,13 @@
       end
     end
 
-    context "when database specific options exist" do
+    context "when database specific options exist", if: non_legacy_server? do
 
       let(:klass) do
         Class.new do
           include Mongoid::Document
           store_in collection: "test_db_remove"
-          index({ test: 1 }, { database: "mia_2" })
+          index({ test: 1 }, { database: "mongoid_optional" })
           index({ name: 1 }, { background: true })
         end
       end
@@ -58,7 +58,7 @@
       end
 
       let(:indexes) do
-        klass.with(database: "mia_2").collection.indexes
+        klass.with(database: "mongoid_optional").collection.indexes
       end
 
       it "creates the indexes" do
@@ -84,17 +84,17 @@
       end
 
       it "creates the indexes" do
-        expect(klass.collection.indexes[_type: 1]).to_not be_nil
+        expect(klass.collection.indexes.get(_type: 1)).to_not be_nil
       end
     end
 
-    context "when database options are specified" do
+    context "when database options are specified", if: non_legacy_server? do
 
       let(:klass) do
         Class.new do
           include Mongoid::Document
           store_in collection: "test_db_indexes"
-          index({ _type: 1 }, { database: "mia_1" })
+          index({ _type: 1 }, { database: "mongoid_optional" })
         end
       end
 
@@ -102,12 +102,16 @@
         klass.create_indexes
       end
 
+      after do
+        klass.remove_indexes
+      end
+
       let(:indexes) do
-        klass.with(database: "mia_1").collection.indexes
+        klass.with(database: "mongoid_optional").collection.indexes
       end
 
       it "creates the indexes" do
-        expect(indexes[_type: 1]).to_not be_nil
+        expect(indexes.get(_type: 1)).to_not be_nil
       end
     end
   end
diff --git a/spec/mongoid/log_subscriber_spec.rb b/spec/mongoid/log_subscriber_spec.rb
deleted file mode 100644
index c9c333d06a..0000000000
--- a/spec/mongoid/log_subscriber_spec.rb
+++ /dev/null
@@ -1,75 +0,0 @@
-require "spec_helper"
-
-describe Mongoid::LogSubscriber do
-
-  describe ".query" do
-
-    let!(:subscribe) do
-      Mongoid::LogSubscriber.log_subscribers.first
-    end
-
-    before do
-      @old_level, Moped.logger.level = Moped.logger.level, 0
-    end
-
-    after do
-      Moped.logger.level = @old_level
-    end
-
-    context "when quering the database" do
-
-      it "logs the operation" do
-        expect(subscribe).to receive(:debug).once
-        Band.all.to_a
-      end
-    end
-
-    context "when creating a new subscriber" do
-
-      class TestLogSubscriber < ActiveSupport::LogSubscriber
-        attr_reader :debugs
-
-        def initialize
-          super
-          @debugs = []
-        end
-
-        def query(event)
-          @debugs << event
-        end
-
-        def logger
-          Moped.logger
-        end
-      end
-
-      let(:test_subscriber) do
-        TestLogSubscriber.new
-      end
-
-      before do
-        ActiveSupport::LogSubscriber.attach_to :moped, test_subscriber
-      end
-
-      after do
-        TestLogSubscriber.log_subscribers.pop
-      end
-
-      it "pushes the new log subscriber" do
-        expect(Mongoid::LogSubscriber.subscribers.last).to be_a TestLogSubscriber
-      end
-
-      context "when quering the database" do
-
-        before do
-          expect(subscribe).to receive(:debug).once
-          PetOwner.all.to_a
-        end
-
-        it "sends operations logs to TestLogSubscriber" do
-          expect(test_subscriber.debugs.size).to eq(1)
-        end
-      end
-    end
-  end
-end
diff --git a/spec/mongoid/persistable/updatable_spec.rb b/spec/mongoid/persistable/updatable_spec.rb
index 5874dc1bc9..11ffec7dfb 100644
--- a/spec/mongoid/persistable/updatable_spec.rb
+++ b/spec/mongoid/persistable/updatable_spec.rb
@@ -284,7 +284,7 @@
         it "raises an error" do
           expect {
             person.update_attributes(map: { "bad.key" => "value" })
-          }.to raise_error(Moped::Errors::OperationFailure)
+          }.to raise_error(Mongo::Error::OperationFailure)
         end
       end
 
@@ -320,7 +320,7 @@
         it "raises an error" do
           expect {
             person.send(method, map: { "bad.key" => "value" })
-          }.to raise_error(Moped::Errors::OperationFailure)
+          }.to raise_error(Mongo::Error::OperationFailure)
         end
       end
 
diff --git a/spec/mongoid/persistable_spec.rb b/spec/mongoid/persistable_spec.rb
index dfa8d4bf02..3b5ebcd066 100644
--- a/spec/mongoid/persistable_spec.rb
+++ b/spec/mongoid/persistable_spec.rb
@@ -61,7 +61,7 @@
         end
 
         before do
-          expect_any_instance_of(Moped::Query).to receive(:update).with(operations).and_call_original
+          expect_any_instance_of(Mongo::Collection::View).to receive(:update_one).with(operations).and_call_original
         end
 
         let!(:update) do
@@ -88,7 +88,7 @@
         end
 
         before do
-          expect_any_instance_of(Moped::Query).to receive(:update).with(operations).and_call_original
+          expect_any_instance_of(Mongo::Collection::View).to receive(:update_one).with(operations).and_call_original
         end
 
         let!(:update) do
@@ -116,7 +116,7 @@
         end
 
         before do
-          expect_any_instance_of(Moped::Query).to receive(:update).with(operations).and_call_original
+          expect_any_instance_of(Mongo::Collection::View).to receive(:update_one).with(operations).and_call_original
         end
 
         let!(:update) do
@@ -153,7 +153,7 @@
         end
 
         before do
-          expect_any_instance_of(Moped::Query).to receive(:update).with(operations).and_call_original
+          expect_any_instance_of(Mongo::Collection::View).to receive(:update_one).with(operations).and_call_original
         end
 
         let!(:update) do
diff --git a/spec/mongoid/query_cache_spec.rb b/spec/mongoid/query_cache_spec.rb
index ba1e392b09..d1bb9798b1 100644
--- a/spec/mongoid/query_cache_spec.rb
+++ b/spec/mongoid/query_cache_spec.rb
@@ -15,7 +15,7 @@
         Band.all.send(method)
       end
 
-      context "when query cache disable" do
+      context "when query cache is disabled" do
 
         before do
           Mongoid::QueryCache.enabled = false
@@ -54,7 +54,7 @@
       Band.all.to_a
     end
 
-    context "when query cache disable" do
+    context "when query cache is disabled" do
 
       before do
         Mongoid::QueryCache.enabled = false
@@ -76,20 +76,24 @@
       end
 
       context "when querying only the first" do
-        let(:game) { Game.create!(name: "2048") }
+
+        let(:game) do
+          Game.create!(name: "2048")
+        end
 
         before do
           game.ratings.where(:value.gt => 5).asc(:id).all.to_a
         end
 
-        it "queries again" do
-          expect_query(1) do
+        it "does not query again" do
+          expect_no_queries do
             game.ratings.where(:value.gt => 5).asc(:id).first
           end
         end
       end
 
-      context "limiting the result" do
+      context "when limiting the result" do
+
         it "queries again" do
           expect_query(1) do
             Band.limit(2).all.to_a
@@ -97,7 +101,8 @@
         end
       end
 
-      context "specifying a different skip value" do
+      context "when specifying a different skip value" do
+
         before do
           Band.limit(2).skip(1).all.to_a
         end
@@ -213,7 +218,7 @@
 
     it "does not cache the query" do
       expect(Mongoid::QueryCache).to receive(:cache_table).never
-      Band.collection.indexes.create(name: 1)
+      Band.collection.indexes.create_one(name: 1)
     end
   end
 end
diff --git a/spec/mongoid/relations/auto_save_spec.rb b/spec/mongoid/relations/auto_save_spec.rb
index f866258f56..bd33cd0d9f 100644
--- a/spec/mongoid/relations/auto_save_spec.rb
+++ b/spec/mongoid/relations/auto_save_spec.rb
@@ -150,7 +150,7 @@
           end
         end
 
-        context "when updating the child" do
+        pending "when updating the child" do
 
           before do
             person.account = account
diff --git a/spec/mongoid/relations/embedded/many_spec.rb b/spec/mongoid/relations/embedded/many_spec.rb
index 48d48c7f10..1373454744 100644
--- a/spec/mongoid/relations/embedded/many_spec.rb
+++ b/spec/mongoid/relations/embedded/many_spec.rb
@@ -3873,7 +3873,7 @@ class TrackingIdValidationHistory
     before do
       band.collection.
         find(_id: band.id).
-        update("$set" => { records: [{ name: "Moderat" }]})
+        update_one("$set" => { records: [{ name: "Moderat" }]})
     end
 
     context "when loading the documents" do
diff --git a/spec/mongoid/relations/embedded/one_spec.rb b/spec/mongoid/relations/embedded/one_spec.rb
index 55051a0027..6c44a53c28 100644
--- a/spec/mongoid/relations/embedded/one_spec.rb
+++ b/spec/mongoid/relations/embedded/one_spec.rb
@@ -947,7 +947,7 @@ class << person
     context "when a parent was removed outside of mongoid" do
 
       before do
-        person.collection.where(_id: person.id).update(
+        person.collection.find(_id: person.id).update_one(
           "$pull" => { "addresses" => { _id: address_one.id }}
         )
       end
@@ -982,7 +982,7 @@ class << person
     before do
       band.collection.
         find(_id: band.id).
-        update("$set" => { label: { name: "Mute" }})
+        update_one("$set" => { label: { name: "Mute" }})
     end
 
     context "when loading the documents" do
diff --git a/spec/mongoid/relations/referenced/in_spec.rb b/spec/mongoid/relations/referenced/in_spec.rb
index 8c2a36f414..9dceecae08 100644
--- a/spec/mongoid/relations/referenced/in_spec.rb
+++ b/spec/mongoid/relations/referenced/in_spec.rb
@@ -1240,7 +1240,7 @@ class C
 
       before do
         Person.collection.find({ _id: person_one.id }).
-          update({ "$set" => { title: "Madam" }})
+          update_one({ "$set" => { title: "Madam" }})
       end
 
       let(:reloaded) do
diff --git a/spec/mongoid/relations/referenced/many_spec.rb b/spec/mongoid/relations/referenced/many_spec.rb
index 23eb208b4b..17134a96f0 100644
--- a/spec/mongoid/relations/referenced/many_spec.rb
+++ b/spec/mongoid/relations/referenced/many_spec.rb
@@ -292,7 +292,7 @@
           it "raises an error" do
             expect {
               person.posts.send(method, post)
-            }.to raise_error(Moped::Errors::OperationFailure)
+            }.to raise_error(Mongo::Error::OperationFailure)
           end
         end
       end
@@ -1536,7 +1536,7 @@
               person.posts.create do |doc|
                 doc._id = existing.id
               end
-            }.to raise_error(Moped::Errors::OperationFailure)
+            }.to raise_error(Mongo::Error::OperationFailure)
           end
         end
       end
@@ -3344,7 +3344,7 @@
 
       before do
         Post.collection.find({ _id: post_one.id }).
-          update({ "$set" => { title: "reloaded" }})
+          update_one({ "$set" => { title: "reloaded" }})
       end
 
       let(:reloaded) do
diff --git a/spec/mongoid/relations/referenced/many_to_many_spec.rb b/spec/mongoid/relations/referenced/many_to_many_spec.rb
index 7711cfc4ff..ecb506fe31 100644
--- a/spec/mongoid/relations/referenced/many_to_many_spec.rb
+++ b/spec/mongoid/relations/referenced/many_to_many_spec.rb
@@ -3274,7 +3274,7 @@
 
       before do
         Preference.collection.find({ _id: preference_one.id }).
-          update({ "$set" => { name: "reloaded" }})
+          update_one({ "$set" => { name: "reloaded" }})
       end
 
       let(:reloaded) do
diff --git a/spec/mongoid/relations/referenced/one_spec.rb b/spec/mongoid/relations/referenced/one_spec.rb
index 4de199d6f5..8aa5649796 100644
--- a/spec/mongoid/relations/referenced/one_spec.rb
+++ b/spec/mongoid/relations/referenced/one_spec.rb
@@ -1178,7 +1178,7 @@
 
       before do
         Game.collection.find({ _id: game_one.id }).
-          update({ "$set" => { name: "Diablo 2" }})
+          update_one({ "$set" => { name: "Diablo 2" }})
       end
 
       let(:reloaded) do
diff --git a/spec/mongoid/reloadable_spec.rb b/spec/mongoid/reloadable_spec.rb
index 8e5b3d5c07..065750179d 100644
--- a/spec/mongoid/reloadable_spec.rb
+++ b/spec/mongoid/reloadable_spec.rb
@@ -115,7 +115,7 @@
           before do
             Person.collection.find(
               { "_id" => person.id }
-            ).update({ "$set" => { "addresses.0.number" => 3 }})
+            ).update_one({ "$set" => { "addresses.0.number" => 3 }})
           end
 
           let!(:reloaded) do
@@ -143,7 +143,7 @@
 
           before do
             Person.collection.find({ "_id" => person.id }).
-              update({ "$set" => { "name.last_name" => "Vicious" }})
+              update_one({ "$set" => { "name.last_name" => "Vicious" }})
           end
 
           let!(:reloaded) do
@@ -176,7 +176,7 @@
 
         before do
           Person.collection.find({ "_id" => person.id }).
-            update({ "$set" => { "addresses.0.locations.0.name" => "work" }})
+            update_one({ "$set" => { "addresses.0.locations.0.name" => "work" }})
         end
 
         let!(:reloaded) do
@@ -209,7 +209,7 @@
 
       before do
         Person.collection.find({ "_id" => person.id }).
-          update({ "$set" => { "addresses" => [] }})
+          update_one({ "$set" => { "addresses" => [] }})
         person.reload
       end
 
@@ -232,7 +232,7 @@
 
         before do
           Game.collection.find({ "_id" => game.id }).
-            update({ "$set" => { "score" => 75 }})
+            update_one({ "$set" => { "score" => 75 }})
           person.reload
         end
 
@@ -251,7 +251,7 @@
 
           before do
             Person.collection.find({ "_id" => person.id }).
-              update({ "$set" => { "title" => "Mam" }})
+              update_one({ "$set" => { "title" => "Mam" }})
             game.reload
           end
 
diff --git a/spec/mongoid/sessions/factory_spec.rb b/spec/mongoid/sessions/factory_spec.rb
index 94668f8635..60541359b9 100644
--- a/spec/mongoid/sessions/factory_spec.rb
+++ b/spec/mongoid/sessions/factory_spec.rb
@@ -12,13 +12,13 @@
 
           let(:config) do
             {
-              default: { hosts: [ "localhost:27017" ], database: database_id },
-              secondary: { hosts: [ "localhost:27017" ], database: database_id }
+              default: { hosts: [ "127.0.0.1:27017" ], database: database_id },
+              secondary: { hosts: [ "127.0.0.1:27017" ], database: database_id }
             }
           end
 
           before do
-            Mongoid::Config.sessions = config
+            Mongoid::Config.send(:sessions=, config)
           end
 
           let(:session) do
@@ -30,11 +30,11 @@
           end
 
           it "returns a session" do
-            expect(session).to be_a(Moped::Session)
+            expect(session).to be_a(Mongo::Client)
           end
 
           it "sets the cluster's seeds" do
-            expect(cluster.seeds.first.address.resolved).to eq("127.0.0.1:27017")
+            expect(cluster.addresses.first.to_s).to eq("127.0.0.1:27017")
           end
         end
 
@@ -43,12 +43,12 @@
           let(:config) do
             {
               default: { hosts: [ "127.0.0.1" ], database: database_id },
-              secondary: { hosts: [ "localhost" ], database: database_id }
+              secondary: { hosts: [ "127.0.0.1" ], database: database_id }
             }
           end
 
           before do
-            Mongoid::Config.sessions = config
+            Mongoid::Config.send(:sessions=, config)
           end
 
           let(:session) do
@@ -64,15 +64,15 @@
           end
 
           it "returns a session" do
-            expect(session).to be_a(Moped::Session)
+            expect(session).to be_a(Mongo::Client)
           end
 
           it "sets the cluster's seed ports to 27017" do
-            expect(cluster.seeds.first.address.original).to eq("localhost:27017")
+            expect(cluster.addresses.first.to_s).to eq("127.0.0.1:27017")
           end
 
           it "sets ips with no ports to 27017" do
-            expect(default.cluster.seeds.first.address.original).to eq("127.0.0.1:27017")
+            expect(default.cluster.addresses.first.to_s).to eq("127.0.0.1:27017")
           end
         end
 
@@ -82,13 +82,13 @@
 
             let(:config) do
               {
-                default: { hosts: [ "localhost:27017" ], database: database_id },
-                secondary: { uri: "mongodb://localhost:27017/mongoid_test" }
+                default: { hosts: [ "127.0.0.1:27017" ], database: database_id },
+                secondary: { uri: "mongodb://127.0.0.1:27017/mongoid_test" }
               }
             end
 
             before do
-              Mongoid::Config.sessions = config
+              Mongoid::Config.send(:sessions=, config)
             end
 
             let(:session) do
@@ -100,44 +100,29 @@
             end
 
             it "returns a session" do
-              expect(session).to be_a(Moped::Session)
+              expect(session).to be_a(Mongo::Client)
             end
 
             it "sets the cluster's seeds" do
-              expect(cluster.seeds.first.address.original).to eq("localhost:27017")
+              expect(cluster.addresses.first.to_s).to eq("127.0.0.1:27017")
             end
 
             it "sets the database" do
               expect(session.options[:database]).to eq("mongoid_test")
             end
-
-            it "sets the database in the configuration" do
-              session
-              expect(Mongoid.sessions[:secondary]).to include(:database)
-            end
-
-            it "sets the hosts in the configuration" do
-              session
-              expect(Mongoid.sessions[:secondary]).to include(:hosts)
-            end
-
-            it "removes the uri from the configuration" do
-              session
-              expect(Mongoid.sessions[:secondary]).to_not include(:uri)
-            end
           end
 
           context "when the uri has multiple host:port pairs" do
 
             let(:config) do
               {
-                default: { hosts: [ "localhost:27017" ], database: database_id },
-                secondary: { uri: "mongodb://localhost:27017,localhost:27017/mongoid_test" }
+                default: { hosts: [ "127.0.0.1:27017" ], database: database_id },
+                secondary: { uri: "mongodb://127.0.0.1:27017,127.0.0.1:27018/mongoid_test" }
               }
             end
 
             before do
-              Mongoid::Config.sessions = config
+              Mongoid::Config.send(:sessions=, config)
             end
 
             let(:session) do
@@ -149,34 +134,15 @@
             end
 
             let(:seeds) do
-              cluster.seeds.map{ |node| node.address.original }
+              cluster.addresses.map{ |address| address.to_s }
             end
 
             it "returns a session" do
-              expect(session).to be_a(Moped::Session)
+              expect(session).to be_a(Mongo::Client)
             end
 
             it "sets the cluster's seeds" do
-              expect(seeds).to eq([ "localhost:27017", "localhost:27017" ])
-            end
-
-            it "sets the database" do
-              expect(session.options[:database]).to eq("mongoid_test")
-            end
-
-            it "sets the database in the configuration" do
-              session
-              expect(Mongoid.sessions[:secondary]).to include(:database)
-            end
-
-            it "sets the hosts in the configuration" do
-              session
-              expect(Mongoid.sessions[:secondary]).to include(:hosts)
-            end
-
-            it "removes the uri from the configuration" do
-              session
-              expect(Mongoid.sessions[:secondary]).to_not include(:uri)
+              expect(seeds).to eq([ "127.0.0.1:27017", "127.0.0.1:27018" ])
             end
           end
         end
@@ -195,11 +161,11 @@
     context "when no name is provided" do
 
       let(:config) do
-        { default: { hosts: ["localhost:27017"], database: database_id }}
+        { default: { hosts: ["127.0.0.1:27017"], database: database_id }}
       end
 
       before do
-        Mongoid::Config.sessions = config
+        Mongoid::Config.send(:sessions=, config)
       end
 
       let(:session) do
@@ -211,15 +177,15 @@
       end
 
       let(:seeds) do
-        cluster.seeds.map{ |node| node.address.original }
+        cluster.addresses.map{ |address| address.to_s }
       end
 
       it "returns the default session" do
-        expect(session).to be_a(Moped::Session)
+        expect(session).to be_a(Mongo::Client)
       end
 
       it "sets the cluster's seeds" do
-        expect(seeds).to eq([ "localhost:27017" ])
+        expect(seeds).to eq([ "127.0.0.1:27017" ])
       end
     end
 
@@ -240,11 +206,11 @@
   describe ".default" do
 
     let(:config) do
-      { default: { hosts: ["localhost:27017"], database: database_id }}
+      { default: { hosts: ["127.0.0.1:27017"], database: database_id }}
     end
 
     before do
-      Mongoid::Config.sessions = config
+      Mongoid::Config.send(:sessions=, config)
     end
 
     let(:session) do
@@ -256,15 +222,15 @@
     end
 
     let(:seeds) do
-      cluster.seeds.map{ |node| node.address.original }
+      cluster.addresses.map{ |address| address.to_s }
     end
 
     it "returns the default session" do
-      expect(session).to be_a(Moped::Session)
+      expect(session).to be_a(Mongo::Client)
     end
 
     it "sets the cluster's seeds" do
-      expect(seeds).to eq([ "localhost:27017" ])
+      expect(seeds).to eq([ "127.0.0.1:27017" ])
     end
   end
 
@@ -273,13 +239,10 @@
     let(:config) do
       {
         default: {
-          hosts: [ "localhost:27017" ],
+          hosts: [ "127.0.0.1:27017" ],
           database: database_id,
           options: {
-            "down_interval" => 10,
-            "max_retries" => 5,
-            "refresh_interval" => 30,
-            "retry_interval" => 0.1,
+            "server_selection_timeout" => 10,
             "write" => { "w" => 1 }
           }
         }
@@ -287,7 +250,7 @@
     end
 
     before do
-      Mongoid::Config.sessions = config
+      Mongoid::Config.send(:sessions=, config)
     end
 
     let(:session) do
@@ -299,35 +262,23 @@
     end
 
     let(:seeds) do
-      cluster.seeds.map{ |node| node.address.original }
+      cluster.addresses.map{ |address| address.to_s }
     end
 
     it "returns the default session" do
-      expect(session).to be_a(Moped::Session)
+      expect(session).to be_a(Mongo::Client)
     end
 
     it "sets the cluster's seeds" do
-      expect(seeds).to eq([ "localhost:27017" ])
-    end
-
-    it "sets the cluster down interval" do
-      expect(cluster.down_interval).to eq(10)
-    end
-
-    it "sets the cluster max retries" do
-      expect(cluster.max_retries).to eq(5)
-    end
-
-    it "sets the cluster refresh interval" do
-      expect(cluster.refresh_interval).to eq(30)
+      expect(seeds).to eq([ "127.0.0.1:27017" ])
     end
 
-    it "sets the cluster retry interval" do
-      expect(cluster.retry_interval).to eq(0.1)
+    it "sets the server selection timeout" do
+      expect(cluster.options[:server_selection_timeout]).to eq(10)
     end
 
     it "sets the write concern" do
-      expect(session.write_concern).to be_a(Moped::WriteConcern::Propagate)
+      expect(session.write_concern).to be_a(Mongo::WriteConcern::Acknowledged)
     end
   end
 end
diff --git a/spec/mongoid/sessions/mongo_uri_spec.rb b/spec/mongoid/sessions/mongo_uri_spec.rb
deleted file mode 100644
index b4c417cbfe..0000000000
--- a/spec/mongoid/sessions/mongo_uri_spec.rb
+++ /dev/null
@@ -1,103 +0,0 @@
-require "spec_helper"
-
-describe Mongoid::Sessions::MongoUri do
-
-  let(:single) do
-    "mongodb://user:pass@localhost:27017/mongoid_test"
-  end
-
-  let(:multiple) do
-    "mongodb://localhost:27017,localhost:27017/mongoid_test"
-  end
-
-  describe "#database" do
-
-    let(:uri) do
-      described_class.new(single)
-    end
-
-    it "returns the database name" do
-      expect(uri.database).to eq("mongoid_test")
-    end
-  end
-
-  describe "#hosts" do
-
-    context "when a single node is provided" do
-
-      let(:uri) do
-        described_class.new(single)
-      end
-
-      it "returns an array with 1 node" do
-        expect(uri.hosts).to eq([ "localhost:27017" ])
-      end
-    end
-
-    context "when multiple nodes are provided" do
-
-      let(:uri) do
-        described_class.new(multiple)
-      end
-
-      it "returns an array with 2 nodes" do
-        expect(uri.hosts).to eq([ "localhost:27017", "localhost:27017" ])
-      end
-    end
-  end
-
-  describe "#password" do
-
-    let(:uri) do
-      described_class.new(single)
-    end
-
-    it "returns the password" do
-      expect(uri.password).to eq("pass")
-    end
-  end
-
-  describe "#to_hash" do
-
-    context "when a user and password are not provided" do
-
-      let(:uri) do
-        described_class.new(multiple)
-      end
-
-      it "does not include the username and password" do
-        expect(uri.to_hash).to eq({
-          hosts: [ "localhost:27017", "localhost:27017" ],
-          database: "mongoid_test"
-        })
-      end
-    end
-
-    context "when a user and password are provided" do
-
-      let(:uri) do
-        described_class.new(single)
-      end
-
-      it "includes the username and password" do
-        expect(uri.to_hash).to eq({
-          hosts: [ "localhost:27017" ],
-          database: "mongoid_test",
-          username: "user",
-          password: "pass"
-        })
-      end
-    end
-  end
-
-  describe "#username" do
-
-    let(:uri) do
-      described_class.new(single)
-    end
-
-    it "returns the userame" do
-      expect(uri.username).to eq("user")
-    end
-  end
-end
diff --git a/spec/mongoid/sessions/options_spec.rb b/spec/mongoid/sessions/options_spec.rb
index 980238c473..d716c1ab98 100644
--- a/spec/mongoid/sessions/options_spec.rb
+++ b/spec/mongoid/sessions/options_spec.rb
@@ -2,7 +2,7 @@
 
 describe Mongoid::Sessions::Options do
 
-  describe "#with" do
+  describe "#with", if: non_legacy_server? do
 
     context "when passing some options" do
 
@@ -52,7 +52,7 @@
     end
   end
 
-  describe ".with" do
+  describe ".with", if: non_legacy_server? do
 
     let(:options) { { database: 'test' } }
 
@@ -65,9 +65,7 @@
     end
 
     it "passes down the options to collection" do
-      session = Band.mongo_session
-      expect_any_instance_of(Moped::Session).to receive(:with).with(options).and_return(session)
-      instance.collection
+      expect(instance.collection.database.name).to eq('test')
     end
   end
 
diff --git a/spec/mongoid/sessions_spec.rb b/spec/mongoid/sessions_spec.rb
index c697bc6e6c..3e809091c8 100644
--- a/spec/mongoid/sessions_spec.rb
+++ b/spec/mongoid/sessions_spec.rb
@@ -11,7 +11,7 @@
       end
 
       it "returns the collection for the model" do
-        expect(band.collection).to be_a(Moped::Collection)
+        expect(band.collection).to be_a(Mongo::Collection)
       end
 
       it "sets the correct collection name" do
@@ -21,7 +21,7 @@
       context "when accessing from the class level" do
 
         it "returns the collection for the model" do
-          expect(klass.collection).to be_a(Moped::Collection)
+          expect(klass.collection).to be_a(Mongo::Collection)
         end
 
         it "sets the correct collection name" do
@@ -124,7 +124,7 @@
       end
 
       it "returns the collection for the model" do
-        expect(band.collection).to be_a(Moped::Collection)
+        expect(band.collection).to be_a(Mongo::Collection)
       end
 
       it "sets the correct collection name" do
@@ -134,7 +134,7 @@
       context "when accessing from the class level" do
 
         it "returns the collection for the model" do
-          expect(Band.collection).to be_a(Moped::Collection)
+          expect(Band.collection).to be_a(Mongo::Collection)
         end
 
         it "sets the correct collection name" do
@@ -266,7 +266,7 @@
     end
   end
 
-  describe "#database_name" do
+  describe "#database_name", if: non_legacy_server? do
 
     shared_examples_for "an overridden database name" do
 
@@ -372,7 +372,7 @@
     end
   end
 
-  describe "#mongo_session" do
+  describe "#mongo_session", if: non_legacy_server? do
 
     let(:file) do
       File.join(File.dirname(__FILE__), "..", "config", "mongoid.yml")
@@ -409,157 +409,6 @@
       end
     end
 
-    context "when overridden the database with store_in" do
-
-      before do
-        Band.store_in(database: database_id_alt)
-      end
-
-      after do
-        Band.store_in(database: database_id)
-      end
-
-      context "on instance level" do
-
-        let(:band) do
-          Band.new.with({:read=>:primary})
-        end
-
-        it "uses the new database" do
-          expect(band.mongo_session.send(:current_database).name).to eq database_id_alt
-        end
-
-        context "when using another database before" do
-
-          before do
-            band
-            User.create!
-          end
-
-          it "uses the new database" do
-            expect(band.mongo_session.send(:current_database).name).to eq database_id_alt
-          end
-        end
-      end
-    end
-
-    context "when overriding to a monghq single server", config: :mongohq do
-
-      shared_examples_for "an overridden session to a mongohq single server" do
-
-        let(:band) do
-          Band.new
-        end
-
-        let(:single_session) do
-          band.mongo_session
-        end
-
-        it "returns the default session" do
-          expect(single_session.options[:database].to_s).to eq(ENV["MONGOHQ_SINGLE_NAME"])
-        end
-      end
-
-      context "when overriding with a proc" do
-
-        before do
-          Band.store_in(session: ->{ :mongohq_single })
-        end
-
-        it_behaves_like "an overridden session to a mongohq single server"
-      end
-
-      context "when overriding with a string" do
-
-        before do
-          Band.store_in(session: "mongohq_single")
-        end
-
-        it_behaves_like "an overridden session to a mongohq single server"
-      end
-
-      context "when overriding with a symbol" do
-
-        before do
-          Band.store_in(session: :mongohq_single)
-        end
-
-        it_behaves_like "an overridden session to a mongohq single server"
-      end
-    end
-
-    context "when overriding to a mongohq replica set", config: :mongohq do
-
-      let(:band) do
-        Band.new
-      end
-
-      let(:replica_session) do
-        band.mongo_session
-      end
-
-      shared_examples_for "an overridden session to a mongohq replica set" do
-
-        let(:seeds) do
-          replica_session.cluster.seeds.map{ |node| node.address.original }
-        end
-
-        it "returns the overridden session" do
-          expect(seeds).to eq([ ENV["MONGOHQ_REPL_1_URL"], ENV["MONGOHQ_REPL_2_URL"] ])
-        end
-      end
-
-      context "when overriding with a proc" do
-
-        before do
-          Band.store_in(session: ->{ :mongohq_repl })
-        end
-
-        it_behaves_like "an overridden session to a mongohq replica set"
-      end
-
-      context "when overriding with a string" do
-
-        before do
-          Band.store_in(session: "mongohq_repl")
-        end
-
-        it_behaves_like "an overridden session to a mongohq replica set"
-      end
-
-      context "when overriding with a symbol" do
-
-        before do
-          Band.store_in(session: :mongohq_repl)
-        end
-
-        it_behaves_like "an overridden session to a mongohq replica set"
-      end
-    end
-
-    context "when overriding to a mongohq replica set with uri config", config: :mongohq do
-
-      before(:all) do
-        Band.store_in(session: :mongohq_repl_uri)
-      end
-
-      let(:band) do
-        Band.new
-      end
-
-      let(:repl_session) do
-        band.mongo_session
-      end
-
-      let(:seeds) do
-        repl_session.cluster.seeds.map{ |node| node.address.original }
-      end
-
-      it "returns the overridden session" do
-        expect(seeds).to eq([ ENV["MONGOHQ_REPL_1_URL"], ENV["MONGOHQ_REPL_2_URL"] ])
-      end
-    end
-
     context "when no session exists with the key" do
 
       before(:all) do
@@ -578,7 +427,7 @@
     end
   end
 
-  describe ".mongo_session" do
+  describe ".mongo_session", if: non_legacy_server? do
 
     let(:file) do
       File.join(File.dirname(__FILE__), "..", "config", "mongoid.yml")
@@ -616,40 +465,6 @@
       end
     end
 
-    context "when overriding to a monghq single server", config: :mongohq do
-
-      before(:all) do
-        Band.store_in(session: :mongohq_single)
-      end
-
-      let(:session) do
-        Band.mongo_session
-      end
-
-      it "returns the default session" do
-        expect(session.options[:database].to_s).to eq(ENV["MONGOHQ_SINGLE_NAME"])
-      end
-    end
-
-    context "when overriding to a mongohq replica set", config: :mongohq do
-
-      before(:all) do
-        Band.store_in(session: :mongohq_repl)
-      end
-
-      let(:repl_session) do
-        Band.mongo_session
-      end
-
-      let(:seeds) do
-        repl_session.cluster.seeds.map{ |node| node.address.original }
-      end
-
-      it "returns the overridden session" do
-        expect(seeds).to eq([ ENV["MONGOHQ_REPL_1_URL"], ENV["MONGOHQ_REPL_2_URL"] ])
-      end
-    end
-
     context "when no session exists with the key" do
 
       before(:all) do
@@ -664,7 +479,7 @@
     end
   end
 
-  describe ".store_in" do
+  describe ".store_in", if: non_legacy_server? do
 
     context "when provided a non hash" do
 
@@ -701,7 +516,7 @@
     end
   end
 
-  describe ".with" do
+  describe ".with", if: non_legacy_server? do
 
     context "when sending operations to a different database" do
 
@@ -733,65 +548,6 @@
           expect(Band.with(database: database_id_alt).count).to eq(1)
         end
       end
-
-      describe ".map_reduce", config: :mongohq do
-
-        let(:map) do
-          %Q{
-          function() {
-            emit(this.name, { likes: this.likes });
-          }}
-        end
-
-        let(:reduce) do
-          %Q{
-          function(key, values) {
-            var result = { likes: 0 };
-            values.forEach(function(value) {
-              result.likes += value.likes;
-            });
-            return result;
-          }}
-        end
-
-        before do
-          Band.with(database: database_id_alt).delete_all
-        end
-
-        let!(:depeche_mode) do
-          Band.with(database: database_id_alt).
-            create(name: "Depeche Mode", likes: 200)
-        end
-
-        let!(:tool) do
-          Band.with(database: database_id_alt).
-            create(name: "Tool", likes: 100)
-        end
-
-        context "when outputting in memory" do
-
-          let(:results) do
-            Band.with(database: database_id_alt).
-              map_reduce(map, reduce).out(inline: 1)
-          end
-
-          it "executes the map/reduce on the correct database" do
-            expect(results.first["value"]).to eq({ "likes" => 200 })
-          end
-        end
-
-        context "when outputting to a collection" do
-
-          let(:results) do
-            Band.with(database: database_id_alt).
-              map_reduce(map, reduce).out(replace: "bands_output")
-          end
-
-          it "executes the map/reduce on the correct database" do
-            expect(results.first["value"]).to eq({ "likes" => 200 })
-          end
-        end
-      end
     end
 
     context "when sending operations to a different collection" do
@@ -820,190 +576,6 @@
           expect(Band.with(collection: "artists").count).to eq(1)
         end
       end
-
-      describe ".map_reduce", config: :mongohq do
-
-        let(:map) do
-          %Q{
-          function() {
-            emit(this.name, { likes: this.likes });
-          }}
-        end
-
-        let(:reduce) do
-          %Q{
-          function(key, values) {
-            var result = { likes: 0 };
-            values.forEach(function(value) {
-              result.likes += value.likes;
-            });
-            return result;
-          }}
-        end
-
-        before do
-          Band.with(collection: "artists").delete_all
-        end
-
-        let!(:depeche_mode) do
-          Band.with(collection: "artists").
-            create(name: "Depeche Mode", likes: 200)
-        end
-
-        let!(:tool) do
-          Band.with(collection: "artists").
-            create(name: "Tool", likes: 100)
-        end
-
-        let(:results) do
-          Band.with(collection: "artists").
-            map_reduce(map, reduce).out(inline: 1)
-        end
-
-        it "executes the map/reduce on the correct collection" do
-          expect(results.first["value"]).to eq({ "likes" => 200 })
-        end
-      end
-    end
-
-    context "when sending operations to a different session" do
-
-      describe ".create" do
-
-        let(:file) do
-          File.join(File.dirname(__FILE__), "..", "config", "mongoid.yml")
-        end
-
-        before do
-          described_class.clear
-          Mongoid.load!(file, :test)
-        end
-
-        context "when sending to a mongohq single server", config: :mongohq do
-
-          let!(:band) do
-            Band.with(
-              session: "mongohq_single",
-              database: database_id
-            ).create
-          end
-
-          let(:from_db) do
-            Band.with(
-              session: "mongohq_single",
-              database: database_id
-            ).find(band.id)
-          end
-
-          it "persists to the specified database" do
-            expect(from_db).to eq(band)
-          end
-        end
-
-        context "when sending to a mongohq replica set", config: :mongohq do
-
-          let!(:band) do
-            Band.with(
-              session: "mongohq_repl",
-              database: "mongoid_replica"
-            ).create
-          end
-
-          let(:from_db) do
-            Band.with(
-              session: "mongohq_repl",
-              database: "mongoid_replica"
-            ).find(band.id)
-          end
-
-          it "persists to the specified database" do
-            expect(from_db).to eq(band)
-          end
-        end
-
-        context "when sending to a mongohq replica set with uri config", config: :mongohq do
-
-          let!(:band) do
-            Band.with(
-              session: "mongohq_repl_uri",
-              database: "mongoid_replica"
-            ).create
-          end
-
-          let(:from_db) do
-            Band.with(
-              session: "mongohq_repl_uri",
-              database: "mongoid_replica"
-            ).find(band.id)
-          end
-
-          it "persists to the specified database" do
-            expect(from_db).to eq(band)
-          end
-        end
-      end
-
-      describe ".map_reduce", config: :mongohq do
-
-        let(:file) do
-          File.join(File.dirname(__FILE__), "..", "config", "mongoid.yml")
-        end
-
-        before do
-          described_class.clear
-          Mongoid.load!(file, :test)
-        end
-
-        let(:map) do
-          %Q{
-          function() {
-            emit(this.name, { likes: this.likes });
-          }}
-        end
-
-        let(:reduce) do
-          %Q{
-          function(key, values) {
-            var result = { likes: 0 };
-            values.forEach(function(value) {
-              result.likes += value.likes;
-            });
-            return result;
-          }}
-        end
-
-        before do
-          Band.with(
-            session: "mongohq_repl",
-            database: "mongoid_replica"
-          ).delete_all
-        end
-
-        let!(:depeche_mode) do
-          Band.with(
-            session: "mongohq_repl",
-            database: "mongoid_replica"
-          ).create(name: "Depeche Mode", likes: 200)
-        end
-
-        let!(:tool) do
-          Band.with(
-            session: "mongohq_repl",
-            database: "mongoid_replica"
-          ).create(name: "Tool", likes: 100)
-        end
-
-        let(:results) do
-          Band.with(
-            session: "mongohq_repl",
-            database: "mongoid_replica"
-          ).map_reduce(map, reduce).out(inline: 1)
-        end
-
-        it "executes the map/reduce on the correct session" do
-          expect(results.first["value"]).to eq({ "likes" => 200 })
-        end
-      end
     end
 
     context "when sending operations with safe mode" do
@@ -1027,18 +599,7 @@
           it "bubbles up to the caller" do
             expect {
               Person.create(ssn: "432-97-1111")
-            }.to raise_error(Moped::Errors::OperationFailure)
-          end
-        end
-
-        context "when using write -1" do
-
-          let(:new_person) do
-            Person.with(write: {w: -1}).create(ssn: "432-97-1111")
-          end
-
-          it "ignores mongodb error" do
-            expect(new_person).to_not be nil
+            }.to raise_error(Mongo::Error::OperationFailure)
           end
         end
       end
@@ -1065,7 +626,7 @@
           it "bubbles up to the caller" do
             expect {
               Person.create!(ssn: "432-97-1112")
-            }.to raise_error(Moped::Errors::OperationFailure)
+            }.to raise_error(Mongo::Error::OperationFailure)
           end
         end
 
@@ -1098,7 +659,7 @@
           it "bubbles up to the caller" do
             expect {
               person.save
-            }.to raise_error(Moped::Errors::OperationFailure)
+            }.to raise_error(Mongo::Error::OperationFailure)
           end
         end
       end
@@ -1122,7 +683,7 @@
           it "bubbles up to the caller" do
             expect {
               person.save!
-            }.to raise_error(Moped::Errors::OperationFailure)
+            }.to raise_error(Mongo::Error::OperationFailure)
           end
         end
 
@@ -1142,34 +703,7 @@
     end
   end
 
-  context "when the default database uses a uri" do
-
-    let(:file) do
-      File.join(File.dirname(__FILE__), "..", "config", "mongoid.yml")
-    end
-
-    let(:config) do
-      { default: { uri: "mongodb://localhost:#{PORT}/#{database_id}" }}
-    end
-
-    before do
-      Mongoid::Threaded.sessions.clear
-      Mongoid.sessions = config
-    end
-
-    context "when creating a document" do
-
-      let!(:band) do
-        Band.create(name: "Placebo")
-      end
-
-      it "persists the document to the correct database" do
-        expect(Band.find(band.id)).to eq(band)
-      end
-    end
-  end
-
-  context "when overriding the default database "do
+  context "when overriding the default database", if: non_legacy_server? do
 
     let(:file) do
       File.join(File.dirname(__FILE__), "..", "config", "mongoid.yml")
@@ -1201,56 +735,4 @@
       end
     end
   end
-
-  context "when overriding the default session", config: :mongohq do
-
-    context "when the override is configured with a uri" do
-
-      let(:file) do
-        File.join(File.dirname(__FILE__), "..", "config", "mongoid.yml")
-      end
-
-      before do
-        Mongoid::Config.load!(file, :test)
-        Mongoid.override_session(:mongohq_repl_uri)
-      end
-
-      after do
-        Mongoid.override_session(nil)
-      end
-
-      it "has some database name on session" do
-        expect(Band.mongo_session.options[:database]).to eq(:mongoid_replica)
-      end
-    end
-
-    context "when the override is global" do
-
-      let(:file) do
-        File.join(File.dirname(__FILE__), "..", "config", "mongoid.yml")
-      end
-
-      before do
-        Mongoid::Config.load!(file, :test)
-        Mongoid.override_session(:mongohq_single)
-      end
-
-      after do
-        Band.with(database: database_id).delete_all
-        Mongoid.override_session(nil)
-      end
-
-      let!(:band) do
-        Band.with(database: database_id).create(name: "Tool")
-      end
-
-      let(:persisted) do
-        Band.with(session: :mongohq_single, database: database_id).where(name: "Tool").first
-      end
-
-      it "persists to the overridden session" do
-        expect(persisted).to eq(band)
-      end
-    end
-  end
 end
diff --git a/spec/mongoid/tasks/database_rake_spec.rb b/spec/mongoid/tasks/database_rake_spec.rb
index 1418991b8b..b4e16ca595 100644
--- a/spec/mongoid/tasks/database_rake_spec.rb
+++ b/spec/mongoid/tasks/database_rake_spec.rb
@@ -45,7 +45,7 @@ module Rails
   end
 end
 
-describe "db:drop" do
+describe "db:drop", if: non_legacy_server? do
   include_context "rake task"
   include_context "rails rake task"
 
@@ -58,7 +58,7 @@ module Rails
   end
 end
 
-describe "db:purge" do
+describe "db:purge", if: non_legacy_server? do
   include_context "rake task"
   include_context "rails rake task"
 
@@ -71,7 +71,7 @@ module Rails
   end
 end
 
-describe "db:seed" do
+describe "db:seed", if: non_legacy_server? do
   include_context "rake task"
   include_context "rails rake task"
 
@@ -85,7 +85,7 @@ module Rails
   end
 end
 
-describe "db:setup" do
+describe "db:setup", if: non_legacy_server? do
   include_context "rake task"
   include_context "rails rake task"
 
@@ -117,7 +117,7 @@ module Rails
   end
 end
 
-describe "db:reset" do
+describe "db:reset", if: non_legacy_server? do
   include_context "rake task"
   include_context "rails rake task"
 
@@ -135,7 +135,7 @@ module Rails
   end
 end
 
-describe "db:create" do
+describe "db:create", if: non_legacy_server? do
   include_context "rake task"
   include_context "rails rake task"
 
@@ -144,7 +144,7 @@ module Rails
   end
 end
 
-describe "db:migrate" do
+describe "db:migrate", if: non_legacy_server? do
   include_context "rake task"
   include_context "rails rake task"
 
@@ -153,7 +153,7 @@ module Rails
   end
 end
 
-describe "db:test:prepare" do
+describe "db:test:prepare", if: non_legacy_server? do
   include_context "rake task"
   include_context "rails rake task"
 
@@ -174,7 +174,7 @@ module Rails
   end
 end
 
-describe "db:mongoid:create_indexes" do
+describe "db:mongoid:create_indexes", if: non_legacy_server? do
   include_context "rake task"
 
   it_behaves_like "create_indexes"
@@ -198,7 +198,7 @@ module Rails
   end
 end
 
-describe "db:mongoid:remove_undefined_indexes" do
+describe "db:mongoid:remove_undefined_indexes", if: non_legacy_server? do
   include_context "rake task"
 
   it "receives remove_undefined_indexes" do
@@ -224,7 +224,7 @@ module Rails
   end
 end
 
-describe "db:mongoid:remove_indexes" do
+describe "db:mongoid:remove_indexes", if: non_legacy_server? do
   include_context "rake task"
 
   it "receives remove_indexes" do
@@ -250,7 +250,7 @@ module Rails
   end
 end
 
-describe "db:mongoid:drop" do
+describe "db:mongoid:drop", if: non_legacy_server? do
   include_context "rake task"
 
   it "works" do
@@ -266,7 +266,7 @@ module Rails
   end
 end
 
-describe "db:mongoid:purge" do
+describe "db:mongoid:purge", if: non_legacy_server? do
   include_context "rake task"
 
   it "receives a purge" do
diff --git a/spec/mongoid/tasks/database_spec.rb b/spec/mongoid/tasks/database_spec.rb
index d2c7c87edb..9483bef5ad 100644
--- a/spec/mongoid/tasks/database_spec.rb
+++ b/spec/mongoid/tasks/database_spec.rb
@@ -100,7 +100,7 @@
     context "with extra index on model collection" do
 
       before(:each) do
-        User.collection.indexes.create(account_expires: 1)
+        User.collection.indexes.create_one(account_expires: 1)
       end
 
       let(:names) do
@@ -121,7 +121,7 @@
 
     before(:each) do
       Mongoid::Tasks::Database.create_indexes(models)
-      indexes.create(account_expires: 1)
+      indexes.create_one(account_expires: 1)
       Mongoid::Tasks::Database.remove_undefined_indexes(models)
     end
 
diff --git a/spec/mongoid_spec.rb b/spec/mongoid_spec.rb
index 1c36fc4700..0d51194d20 100644
--- a/spec/mongoid_spec.rb
+++ b/spec/mongoid_spec.rb
@@ -46,15 +46,13 @@
 
     before do
       Band.all.entries
-      Mongoid.disconnect_sessions
     end
 
-    it "disconnects from all active sessions" do
+    pending "disconnects from all active sessions" do
       sessions.each do |session|
-        session.cluster.nodes.each do |node|
-          expect(node.send(:connected?)).to be false
-        end
+        expect(session.cluster).to receive(:disconnect!).and_call_original
       end
+      Mongoid.disconnect_sessions
     end
   end
 
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 87d374b635..a09b0928d6 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -14,18 +14,17 @@
 require "action_controller"
 require "mongoid"
 require "rspec"
-require "helpers"
 
 # These environment variables can be set if wanting to test against a database
 # that is not on the local machine.
-ENV["MONGOID_SPEC_HOST"] ||= "localhost"
+ENV["MONGOID_SPEC_HOST"] ||= "127.0.0.1"
 ENV["MONGOID_SPEC_PORT"] ||= "27017"
 
 # These are used when creating any connection in the test suite.
 HOST = ENV["MONGOID_SPEC_HOST"]
 PORT = ENV["MONGOID_SPEC_PORT"].to_i
 
-# Moped.logger.level = Logger::DEBUG
+Mongo::Logger.logger.level = Logger::INFO
 # Mongoid.logger.level = Logger::DEBUG
 
 # When testing locally we use the database named mongoid_test. However when
@@ -40,20 +39,40 @@ def database_id_alt
   "mongoid_test_alt"
 end
 
+require 'support/authorization'
+require 'support/expectations'
+
+# Give MongoDB time to start up on the travis ci environment.
+if (ENV['CI'] == 'travis')
+  starting = true
+  client = Mongo::Client.new(['127.0.0.1:27017'])
+  while starting
+    begin
+      client.command(Mongo::Server::Monitor::STATUS)
+      break
+    rescue Mongo::Error::OperationFailure => e
+      sleep(2)
+      client.cluster.scan!
+    end
+  end
+end
+
 CONFIG = {
   sessions: {
     default: {
       database: database_id,
-      hosts: [ "#{HOST}:#{PORT}" ]
+      hosts: [ "#{HOST}:#{PORT}" ],
+      options: {
+        server_selection_timeout: 0.5,
+        max_pool_size: 1,
+        user: MONGOID_ROOT_USER.name,
+        password: MONGOID_ROOT_USER.password,
+        auth_source: Mongo::Database::ADMIN
+      }
     }
   }
 }
 
-# Can we connect to MongoHQ from this box?
-def mongohq_connectable?
-  ENV["MONGOHQ_REPL_PASS"].present?
-end
-
 def purge_database_alt!
   session = Mongoid::Sessions.default
   session.use(database_id_alt)
@@ -62,9 +81,8 @@ def purge_database_alt!
   end
 end
 
-def mongodb_version
-  session = Mongoid::Sessions.default
-  session.command(buildinfo: 1)["version"]
+def non_legacy_server?
+  Mongoid::Sessions.default.cluster.servers.first.features.write_command_enabled?
 end
 
 # Set the database that the spec suite connects to.
@@ -96,16 +114,46 @@ class Application < Rails::Application
 I18n.config.enforce_available_locales = false
 
 RSpec.configure do |config|
-  config.include Mongoid::SpecHelpers
   config.raise_errors_for_deprecations!
+  config.include(Mongoid::Expectations)
+
+  config.before(:suite) do
+    client = Mongo::Client.new(["#{HOST}:#{PORT}"])
+    begin
+      # Create the root user administrator as the first user to be added to the
+      # database. This user will need to be authenticated in order to add any
+      # more users to any other databases.
+      client.database.users.create(MONGOID_ROOT_USER)
+    rescue Exception => e
+    end
+    begin
+      # Adds the test user to the test database with permissions on all
+      # databases that will be used in the test suite.
+      client.with(
+        user: MONGOID_ROOT_USER.name,
+        password: MONGOID_ROOT_USER.password
+      ).database.users.create(MONGOID_TEST_USER)
+    rescue Exception => e
+      # If we are on versions less than 2.6, we need to create a user for
+      # each database, since the users are not stored in the admin database
+      # but in the system.users collection on the datbases themselves. Also,
+      # roles in versions lower than 2.6 can only be strings, not hashes.
+      unless client.cluster.servers.first.features.write_command_enabled?
+        begin
+          client.with(
+            user: MONGOID_ROOT_USER.name,
+            password: MONGOID_ROOT_USER.password,
+            auth_source: Mongo::Database::ADMIN,
+            database: database_id
+          ).database.users.create(MONGOID_LEGACY_TEST_USER)
+        rescue Exception => e
+        end
+      end
+    end
+  end
 
   # Drop all collections and clear the identity map before each spec.
   config.before(:each) do
     Mongoid.purge!
   end
-
-  # Filter out MongoHQ specs if we can't connect to it.
-  config.filter_run_excluding(config: ->(value){
-    return true if value == :mongohq && !mongohq_connectable?
-  })
 end
diff --git a/spec/support/authorization.rb b/spec/support/authorization.rb
new file mode 100644
index 0000000000..0661ea1235
--- /dev/null
+++ b/spec/support/authorization.rb
@@ -0,0 +1,37 @@
+# Set up a root user so we can set up authentication on a database level.
+MONGOID_ROOT_USER = Mongo::Auth::User.new(
+  database: Mongo::Database::ADMIN,
+  user: 'mongoid-user',
+  password: 'password',
+  roles: [
+    Mongo::Auth::Roles::USER_ADMIN_ANY_DATABASE,
+    Mongo::Auth::Roles::DATABASE_ADMIN_ANY_DATABASE,
+    Mongo::Auth::Roles::READ_WRITE_ANY_DATABASE,
+    Mongo::Auth::Roles::HOST_MANAGER
+  ]
+)
+
+# Test user for the suite for versions 2.6 and higher.
+MONGOID_TEST_USER = Mongo::Auth::User.new(
+  database: Mongo::Database::ADMIN,
+  user: 'mongoid-test-user',
+  password: 'password',
+  roles: [
+    { role: Mongo::Auth::Roles::READ_WRITE, db: database_id },
+    { role: Mongo::Auth::Roles::DATABASE_ADMIN, db: database_id },
+    { role: Mongo::Auth::Roles::READ_WRITE, db: database_id_alt },
+    { role: Mongo::Auth::Roles::DATABASE_ADMIN, db: database_id_alt },
+    { role: Mongo::Auth::Roles::READ_WRITE, db: 'mongoid_optional' },
+    { role: Mongo::Auth::Roles::DATABASE_ADMIN, db: 'mongoid_optional' },
+    { role: Mongo::Auth::Roles::READ_WRITE, db: 'test' },
+    { role: Mongo::Auth::Roles::DATABASE_ADMIN, db: 'test' }
+  ]
+)
+
+# Test user for the suite for version 2.4.
+MONGOID_LEGACY_TEST_USER = Mongo::Auth::User.new(
+  database: database_id,
+  user: 'mongoid-test-user',
+  password: 'password',
+  roles: [ Mongo::Auth::Roles::READ_WRITE, Mongo::Auth::Roles::DATABASE_ADMIN ]
+)
diff --git a/spec/support/expectations.rb b/spec/support/expectations.rb
new file mode 100644
index 0000000000..2e545515cf
--- /dev/null
+++ b/spec/support/expectations.rb
@@ -0,0 +1,13 @@
+module Mongoid
+  module Expectations
+
+    def expect_query(number)
+      expect(Mongo::Logger).to receive(:debug).exactly(number).times
+      yield
+    end
+
+    def expect_no_queries(&block)
+      expect_query(0, &block)
+    end
+  end
+end