diff --git a/.github/workflows/actions.yml b/.github/workflows/actions.yml
index 54e3ff1..454f9d2 100644
--- a/.github/workflows/actions.yml
+++ b/.github/workflows/actions.yml
@@ -9,7 +9,11 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: [ '2.5', '2.6', '2.7', '3.0', '3.1' ]
+        ruby: [ '3.0', '3.1', '3.2', '3.3' ]
+        task: [ 'spec' ]
+        include:
+        - ruby: '3.0' # keep in sync with rubocop.yml and gemspec
+          task: 'rubocop'
     name: ${{ matrix.ruby }} rake
     steps:
     - uses: actions/checkout@v2
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..75600ff
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,110 @@
+require:
+- rubocop-rake
+- rubocop-rspec
+
+AllCops:
+  NewCops: enable
+  TargetRubyVersion: 3.0 # keep in sync with gemspec and actions.yml
+
+Style/StringLiterals:
+  Enabled: false
+
+Bundler/OrderedGems:
+  Enabled: false
+
+Metrics:
+  Enabled: false
+
+Style/Documentation:
+  Enabled: false
+
+Layout/EmptyLineAfterMagicComment:
+  Enabled: false
+
+Layout/EndAlignment:
+  EnforcedStyleAlignWith: variable
+
+Layout/MultilineOperationIndentation:
+  Enabled: false
+
+Layout/MultilineMethodCallIndentation:
+  EnforcedStyle: indented
+
+Style/NumericPredicate:
+  EnforcedStyle: comparison
+
+Layout/EmptyLineAfterGuardClause:
+  Enabled: false
+
+Layout/FirstHashElementLineBreak:
+  Enabled: true # Opt-in
+
+# Opt-in
+Layout/FirstMethodArgumentLineBreak:
+  Enabled: true # Opt-in
+
+Layout/FirstMethodParameterLineBreak:
+  Enabled: true # Opt-in
+
+# https://github.com/rubocop-hq/rubocop/issues/5891
+Style/SpecialGlobalVars:
+  Enabled: false
+
+Style/WordArray:
+  EnforcedStyle: brackets
+
+Style/SymbolArray:
+  EnforcedStyle: brackets
+
+Style/GuardClause:
+  Enabled: false
+
+Style/EmptyElse:
+  Enabled: false
+
+RSpec/DescribedClass:
+  EnforcedStyle: explicit
+
+Style/DoubleNegation:
+  Enabled: false
+
+RSpec/VerifiedDoubles:
+  Enabled: false
+
+RSpec/ExampleLength:
+  Enabled: false
+
+Style/CombinableLoops:
+  Enabled: false
+
+Lint/Void:
+  Enabled: false
+
+Security/MarshalLoad:
+  Enabled: false
+
+Lint/EmptyBlock:
+  Exclude: [spec/**/*.rb]
+
+Naming/MethodParameterName:
+  Exclude: [spec/**/*.rb]
+
+RSpec/BeforeAfterAll:
+  Enabled: false
+
+# could change to `#method` and `.method` instead
+RSpec/DescribeSymbol:
+  Enabled: false
+
+RSpec/NestedGroups:
+  Enabled: false
+
+RSpec/EmptyExampleGroup:
+  Enabled: false
+
+Lint/SuppressedException:
+  Enabled: false
+
+# somehow crashes
+RSpec/VariableName:
+  Enabled: false
diff --git a/Gemfile b/Gemfile
index edc4b02..7cc83c9 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,6 +1,10 @@
+# frozen_string_literal: true
 source 'https://rubygems.org'
 gemspec
 
 gem 'bump'
 gem 'rake'
 gem 'rspec', '~>3.0'
+gem 'rubocop'
+gem 'rubocop-rake'
+gem 'rubocop-rspec'
diff --git a/Gemfile.lock b/Gemfile.lock
index 519e5b7..b0ba889 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -7,9 +7,21 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
+    ast (2.4.2)
     bump (0.10.0)
     diff-lcs (1.4.4)
+    json (2.7.2)
+    language_server-protocol (3.17.0.3)
+    parallel (1.26.3)
+    parser (3.3.4.2)
+      ast (~> 2.4.1)
+      racc
+    racc (1.8.1)
+    rainbow (3.1.1)
     rake (13.0.6)
+    regexp_parser (2.9.2)
+    rexml (3.3.6)
+      strscan
     rspec (3.10.0)
       rspec-core (~> 3.10.0)
       rspec-expectations (~> 3.10.0)
@@ -23,7 +35,27 @@ GEM
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.10.0)
     rspec-support (3.10.3)
+    rubocop (1.65.1)
+      json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
+      parallel (~> 1.10)
+      parser (>= 3.3.0.2)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 2.4, < 3.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.31.1, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 2.4.0, < 3.0)
+    rubocop-ast (1.32.1)
+      parser (>= 3.3.1.0)
+    rubocop-rake (0.6.0)
+      rubocop (~> 1.0)
+    rubocop-rspec (2.9.0)
+      rubocop (~> 1.19)
+    ruby-progressbar (1.13.0)
     simple_po_parser (1.1.6)
+    strscan (3.1.0)
+    unicode-display_width (2.5.0)
 
 PLATFORMS
   ruby
@@ -36,6 +68,9 @@ DEPENDENCIES
   i18n_data!
   rake
   rspec (~> 3.0)
+  rubocop
+  rubocop-rake
+  rubocop-rspec
 
 BUNDLED WITH
    2.3.12
diff --git a/Rakefile b/Rakefile
index 7bc8692..6a9ed17 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'bundler/setup'
 require 'bundler/gem_tasks'
 require 'bump/tasks'
@@ -6,22 +7,28 @@ require 'yaml'
 $LOAD_PATH << "lib"
 require 'i18n_data'
 
-task default: [:spec]
+task default: [:spec, :rubocop]
 
+desc "Run tests"
 task :spec do
   sh "rspec --warnings spec/"
 end
 
+desc "Rubocop"
+task :rubocop do
+  sh "rubocop --parallel"
+end
+
 desc "write all languages to output"
 task :all_languages do
-  I18nData.languages.keys.each do |lc|
+  I18nData.languages.each_key do |lc|
     `rake languages LANGUAGE=#{lc}`
   end
 end
 
 desc "write languages to output/languages_{language}"
 task :languages do
-  raise unless language = ENV['LANGUAGE']
+  raise unless (language = ENV.fetch('LANGUAGE', nil))
   `mkdir -p output`
   data = I18nData.languages(language.upcase)
   File.write "output/languages_#{language.downcase}.yml", data.to_yaml
@@ -29,34 +36,32 @@ end
 
 desc "write all countries to output to debug"
 task :all_countries do
-  I18nData.languages.keys.each do |lc|
+  I18nData.languages.each_key do |lc|
     `rake countries LANGUAGE=#{lc}`
   end
 end
 
 desc "write countries to output/countries_{language} to debug"
 task :countries do
-  raise unless language = ENV['LANGUAGE']
+  raise unless (language = ENV.fetch('LANGUAGE', nil))
   `mkdir -p output`
   data = I18nData.countries(language.upcase)
-  File.open("output/countries_#{language.downcase}.yml",'w') {|f|f.puts data.to_yaml}
+  File.open("output/countries_#{language.downcase}.yml", 'w') { |f| f.puts data.to_yaml }
 end
 
 desc "write example output, just to show off :D"
 task :example_output do
   `mkdir -p example_output`
 
-  #all names for germany, france, united kingdom and unites states
-  ['DE','FR','GB','US'].each do |cc|
+  # all names for germany, france, united kingdom and unites states
+  ['DE', 'FR', 'GB', 'US'].each do |cc|
     names = I18nData.languages.keys.map do |lc|
-      begin
-        [I18nData.countries(lc)[cc], I18nData.languages[lc]]
-      rescue I18nData::NoTranslationAvailable
-        nil
-      end
+      [I18nData.countries(lc)[cc], I18nData.languages[lc]]
+    rescue I18nData::NoTranslationAvailable
+      nil
     end
-    File.open("example_output/all_names_for_#{cc}.txt",'w') do |f|
-      f.puts names.reject(&:nil?).map{|x|x*" ---- "} * "\n"
+    File.open("example_output/all_names_for_#{cc}.txt", 'w') do |f|
+      f.puts names.compact.map { |x| x * " ---- " } * "\n"
     end
   end
 end
@@ -66,7 +71,7 @@ task :stats do
   dir = "cache/file_data_provider"
   [:languages, :countries].each do |type|
     files = FileList["#{dir}/#{type}*"]
-    lines = File.readlines(files.first).reject{|l|l.empty?}
+    lines = File.readlines(files.first).reject(&:empty?)
     puts "#{lines.size} #{type} in #{files.size} languages"
   end
 end
diff --git a/i18n_data.gemspec b/i18n_data.gemspec
index 8560493..db64fa2 100644
--- a/i18n_data.gemspec
+++ b/i18n_data.gemspec
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 name = "i18n_data"
 require "./lib/#{name}/version"
 
@@ -8,6 +9,6 @@ Gem::Specification.new name, I18nData::VERSION do |s|
   s.homepage = "https://github.com/grosser/#{name}"
   s.files = `git ls-files lib cache `.split("\n")
   s.license = "MIT"
-  s.required_ruby_version = '>= 2.5.0'
-  s.add_runtime_dependency 'simple_po_parser', '~> 1.1'
+  s.required_ruby_version = '>= 3.0.0' # keep in sync with rubocop.yml and actions.yml
+  s.add_dependency 'simple_po_parser', '~> 1.1'
 end
diff --git a/lib/i18n_data.rb b/lib/i18n_data.rb
index 957cded..1098e75 100644
--- a/lib/i18n_data.rb
+++ b/lib/i18n_data.rb
@@ -1,7 +1,7 @@
+# frozen_string_literal: true
 require 'i18n_data/version'
 
 module I18nData
-
   class BaseException < StandardError
     def to_s
       "#{self.class} -- #{super}"
@@ -13,13 +13,13 @@ class AccessDenied < BaseException; end
   class Unknown < BaseException; end
 
   class << self
-    def languages(language_code='EN')
+    def languages(language_code = 'EN')
       fetch :languages, language_code do
         data_provider.codes(:languages, normal_to_region_code(language_code.to_s.upcase))
       end
     end
 
-    def countries(language_code='EN')
+    def countries(language_code = 'EN')
       fetch :countries, language_code do
         data_provider.codes(:countries, normal_to_region_code(language_code.to_s.upcase))
       end
@@ -34,10 +34,10 @@ def language_code(name)
     end
 
     def data_provider
-      @data_provider ||= (
+      @data_provider ||= begin
         require 'i18n_data/file_data_provider'
         FileDataProvider
-      )
+      end
     end
 
     def data_provider=(provider)
@@ -57,7 +57,7 @@ def fetch(type, language_code)
     def normal_to_region_code(normal)
       {
         "ZH" => "zh_CN",
-        "BN" => "bn_IN",
+        "BN" => "bn_IN"
       }[normal] || normal
     end
 
@@ -65,7 +65,7 @@ def recognise_code(type, search)
       search = search.strip
 
       # common languages first <-> faster in majority of cases
-      language_codes = ['EN','ES','FR','DE','ZH'] | available_language_codes
+      language_codes = ['EN', 'ES', 'FR', 'DE', 'ZH'] | available_language_codes
 
       language_codes.each do |language_code|
         options =
@@ -88,8 +88,8 @@ def recognise_code(type, search)
     # NOTE: this is not perfect since the used provider might have more or less languages available
     # but it's better than just using the available english language codes
     def available_language_codes
-      @available_languges ||= begin
-        files = Dir[File.expand_path("../../cache/file_data_provider/languages-*", __FILE__)]
+      @available_language_codes ||= begin
+        files = Dir[File.expand_path('../cache/file_data_provider/languages-*', __dir__)]
         files.map! { |f| f[/languages-(.*)\./, 1] }
       end
     end
diff --git a/lib/i18n_data/file_data_provider.rb b/lib/i18n_data/file_data_provider.rb
index b2be72d..4db6b22 100644
--- a/lib/i18n_data/file_data_provider.rb
+++ b/lib/i18n_data/file_data_provider.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module I18nData
   module FileDataProvider
     require 'fileutils'
@@ -6,7 +7,7 @@ module FileDataProvider
     extend self
 
     def codes(type, language_code)
-      unless data = read_from_file(cache_file_for(type, language_code))
+      unless (data = read_from_file(cache_file_for(type, language_code)))
         raise NoTranslationAvailable, "#{type}-#{language_code}"
       end
       data
@@ -16,14 +17,12 @@ def write_cache(provider)
       languages = provider.codes(:languages, 'EN').keys + ['zh_CN', 'zh_TW', 'zh_HK', 'bn_IN', 'pt_BR', 'sr@latin']
       languages.map do |language_code|
         [:languages, :countries].each do |type|
-          begin
-            data = provider.send(:codes, type, language_code)
-            write_to_file(data, cache_file_for(type, language_code))
-          rescue NoTranslationAvailable
-            $stderr.puts "No translation available for #{type} #{language_code}" if $DEBUG
-          rescue AccessDenied
-            $stderr.puts "Access denied for #{type} #{language_code}"
-          end
+          data = provider.send(:codes, type, language_code)
+          write_to_file(data, cache_file_for(type, language_code))
+        rescue NoTranslationAvailable
+          warn "No translation available for #{type} #{language_code}" if $DEBUG
+        rescue AccessDenied
+          warn "Access denied for #{type} #{language_code}"
         end
       end
     end
@@ -33,7 +32,7 @@ def write_cache(provider)
     def read_from_file(file)
       return nil unless File.exist?(file)
       data = {}
-      File.readlines(file, :encoding => 'utf-8').each do |line|
+      File.readlines(file, encoding: 'utf-8').each do |line|
         code, translation = line.strip.split(DATA_SEPARATOR, 2)
         data[code] = translation
       end
@@ -43,12 +42,10 @@ def read_from_file(file)
     def write_to_file(data, file)
       return if data.empty?
       FileUtils.mkdir_p File.dirname(file)
-      File.open(file,'w') do |f|
-        f.write data.map{|code, translation| "#{code}#{DATA_SEPARATOR}#{translation}" } * "\n"
-      end
+      File.write(file, data.map { |code, translation| "#{code}#{DATA_SEPARATOR}#{translation}" } * "\n")
     end
 
-    def cache_file_for(type,language_code)
+    def cache_file_for(type, language_code)
       file = "#{type}-#{language_code.sub('-', '_').upcase}"
       File.join(File.dirname(__FILE__), '..', '..', 'cache', 'file_data_provider', "#{file}.txt")
     end
diff --git a/lib/i18n_data/live_data_provider.rb b/lib/i18n_data/live_data_provider.rb
index ac27286..eba4f54 100644
--- a/lib/i18n_data/live_data_provider.rb
+++ b/lib/i18n_data/live_data_provider.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'json'
 require 'simple_po_parser'
 
@@ -7,14 +8,14 @@ module LiveDataProvider
     extend self
 
     JSON_CODES = {
-      :countries => 'data/iso_3166-1.json',
-      :languages => 'data/iso_639-2.json'
-    }
+      countries: 'data/iso_3166-1.json',
+      languages: 'data/iso_639-2.json'
+    }.freeze
 
     TRANSLATIONS = {
-      :countries => 'iso_3166-1/',
-      :languages => 'iso_639-2/'
-    }
+      countries: 'iso_3166-1/',
+      languages: 'iso_639-2/'
+    }.freeze
     REPO = "https://salsa.debian.org/iso-codes-team/iso-codes.git"
     CLONE_DEST = "/tmp/i18n_data_iso_clone"
 
@@ -34,7 +35,7 @@ def clear_cache
       raise unless $?.success?
     end
 
-  private
+    private
 
     def ensure_checkout
       unless File.exist?(CLONE_DEST)
@@ -46,10 +47,8 @@ def ensure_checkout
     def translated(type, language_code)
       @translated ||= {}
 
-      @translated["#{type}_#{language_code}"] ||= begin
-        Hash[send("alpha_codes_for_#{type}").map do |alpha2, alpha3|
-          [alpha2, translate(type, alpha3, language_code) || fallback_name(type, alpha3)]
-        end]
+      @translated["#{type}_#{language_code}"] ||= send("alpha_codes_for_#{type}").transform_values do |alpha3|
+        translate(type, alpha3, language_code) || fallback_name(type, alpha3)
       end
     end
 
@@ -68,7 +67,7 @@ def translations(type, language_code)
         begin
           file_path = "#{CLONE_DEST}/#{TRANSLATIONS[type]}#{code}.po"
           data = SimplePoParser.parse(file_path)
-          data = data[1..-1] # Remove the initial info block in the .po file
+          data = data[1..] # Remove the initial info block in the .po file
 
           # Prefer the "Common name for" blocks, but fallback to "Name for" blocks
           common_names = get_po_data(data, 'Common name for')
@@ -90,7 +89,7 @@ def get_po_data(data, extracted_comment_string)
       # Maps over the alpha3 country code in the 'extracted_comment'
       # Eg: "Name for GBR"
       po_entries.map.with_object({}) do |t, translations|
-        alpha3 = t[:extracted_comment][-3..-1].upcase
+        alpha3 = t[:extracted_comment][-3..].upcase
         translation = t[:msgstr]
         translations[alpha3] = translation.is_a?(Array) ? translation.join : translation
       end
@@ -118,7 +117,7 @@ def english_languages
         json(:languages)['639-2'].each do |entry|
           name = entry['name'].to_s
           code = entry['alpha_2'].to_s.upcase
-          next if code.empty? or name.empty?
+          next if code.empty? || name.empty?
           codes[code] = name
         end
         codes
diff --git a/lib/i18n_data/version.rb b/lib/i18n_data/version.rb
index bd6f2db..a4cfa84 100644
--- a/lib/i18n_data/version.rb
+++ b/lib/i18n_data/version.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module I18nData
-  VERSION = Version = "0.17.1"
+  VERSION = Version = "0.17.1" # rubocop:disable Naming/ConstantName
 end
diff --git a/spec/benchmark.rb b/spec/benchmark.rb
index d385392..cc9428f 100644
--- a/spec/benchmark.rb
+++ b/spec/benchmark.rb
@@ -1,10 +1,11 @@
+# frozen_string_literal: true
 # Benchmark performance by looking up every available language's country and
 # language translations multiple times.
 
 require 'benchmark'
 require 'i18n_data'
 
-types = %i(countries languages)
+types = [:countries, :languages]
 
 type_codes = {}
 types.each do |type|
@@ -18,12 +19,10 @@
   10.times do
     type_codes.each_pair do |type, codes|
       codes.each do |code|
-        begin
-          I18nData.send(type, code).keys.each do |key|
-            I18nData.send(type, code)[key]
-          end
-        rescue I18nData::NoTranslationAvailable
+        I18nData.send(type, code).each_key do |key|
+          I18nData.send(type, code)[key]
         end
+      rescue I18nData::NoTranslationAvailable
       end
     end
   end
diff --git a/spec/i18n_data/file_data_provider_spec.rb b/spec/i18n_data/file_data_provider_spec.rb
index face1d0..a23eeeb 100644
--- a/spec/i18n_data/file_data_provider_spec.rb
+++ b/spec/i18n_data/file_data_provider_spec.rb
@@ -1,8 +1,9 @@
+# frozen_string_literal: true
 require "spec_helper"
 require 'i18n_data/file_data_provider'
 
 describe I18nData::FileDataProvider do
-  let(:cache_file) { I18nData::FileDataProvider.send(:cache_file_for,"XX","YY") }
+  let(:cache_file) { I18nData::FileDataProvider.send(:cache_file_for, "XX", "YY") }
 
   around do |test|
     `rm -f #{cache_file}`
@@ -10,29 +11,29 @@
     `rm -f #{cache_file}`
   end
 
-  def read(x,y)
-    I18nData::FileDataProvider.codes(x,y)
+  def read(x, y)
+    I18nData::FileDataProvider.codes(x, y)
   end
 
   it "always produces uppercase locales to avoid case-sensitive madness" do
-    cache_file = I18nData::FileDataProvider.send(:cache_file_for,"countries","yy_YY")
+    cache_file = I18nData::FileDataProvider.send(:cache_file_for, "countries", "yy_YY")
     File.basename(cache_file).should == "countries-YY_YY.txt"
   end
 
   it "always convert hyphen (-) to underscore (_) in locale names" do
-    cache_file = I18nData::FileDataProvider.send(:cache_file_for,"countries","yy-YY")
+    cache_file = I18nData::FileDataProvider.send(:cache_file_for, "countries", "yy-YY")
     File.basename(cache_file).should == "countries-YY_YY.txt"
   end
 
   it "preserves data when writing and then reading" do
-    data = {"x"=>"y","z"=>"w"}
+    data = { "x" => "y", "z" => "w" }
     I18nData::FileDataProvider.send(:write_to_file, data, cache_file)
-    read("XX","YY").should == data
+    read("XX", "YY").should == data
   end
 
   it "does not write empty data sets" do
-    I18nData::FileDataProvider.send(:write_to_file,{}, cache_file)
-    lambda { read("XX","YY") }.should raise_error I18nData::NoTranslationAvailable
+    I18nData::FileDataProvider.send(:write_to_file, {}, cache_file)
+    -> { read("XX", "YY") }.should raise_error I18nData::NoTranslationAvailable
   end
 
   it "reads taiwan correctly" do
diff --git a/spec/i18n_data/live_data_provider_spec.rb b/spec/i18n_data/live_data_provider_spec.rb
index 6071c7e..fe40568 100644
--- a/spec/i18n_data/live_data_provider_spec.rb
+++ b/spec/i18n_data/live_data_provider_spec.rb
@@ -1,7 +1,7 @@
+# frozen_string_literal: true
 require "spec_helper"
 require "i18n_data/live_data_provider"
 
 # fetching is tested via spec/i18n_data_spec.rb, these are just unit-tests
 describe I18nData::LiveDataProvider do
-
 end
diff --git a/spec/i18n_data_spec.rb b/spec/i18n_data_spec.rb
index b86fa06..ccbb47c 100644
--- a/spec/i18n_data_spec.rb
+++ b/spec/i18n_data_spec.rb
@@ -1,4 +1,4 @@
-# encoding: utf-8
+# frozen_string_literal: true
 require "spec_helper"
 
 NUM_2_LETTER_LANGUAGES = 184
@@ -9,7 +9,7 @@
   require "i18n_data/file_data_provider"
 
   def blank_keys_or_values(hash)
-    hash.detect{|k,v| k.to_s.empty? or v.to_s.empty?}
+    hash.detect { |k, v| k.to_s.empty? or v.to_s.empty? }
   end
 
   around do |t|
@@ -40,7 +40,7 @@ def blank_keys_or_values(hash)
 
       describe ".languages" do
         it "raises NoTranslationAvailable for unavailable languages" do
-          lambda{I18nData.languages('XX')}.should raise_error(I18nData::NoTranslationAvailable)
+          -> { I18nData.languages('XX') }.should raise_error(I18nData::NoTranslationAvailable)
         end
 
         it "is cached" do
@@ -51,7 +51,7 @@ def blank_keys_or_values(hash)
 
         describe "english" do
           it "does not contain blanks" do
-            blank_keys_or_values(I18nData.languages).should eq nil
+            blank_keys_or_values(I18nData.languages).should be_nil
           end
 
           it "has english as default" do
@@ -77,7 +77,7 @@ def blank_keys_or_values(hash)
           end
 
           it "does not contain blanks" do
-            blank_keys_or_values(I18nData.languages('GL')).should eq nil
+            blank_keys_or_values(I18nData.languages('GL')).should be_nil
           end
 
           it "is written in unicode" do
@@ -111,7 +111,7 @@ def blank_keys_or_values(hash)
           end
 
           it "does not contain blanks" do
-            blank_keys_or_values(I18nData.countries).should eq nil
+            blank_keys_or_values(I18nData.countries).should be_nil
           end
 
           it "contains all countries" do
@@ -149,7 +149,7 @@ def blank_keys_or_values(hash)
           end
 
           it "does not contain blanks" do
-            blank_keys_or_values(I18nData.countries('GL')).should eq nil
+            blank_keys_or_values(I18nData.countries('GL')).should be_nil
           end
 
           it "is written in unicode" do
@@ -174,8 +174,12 @@ def blank_keys_or_values(hash)
   end
 
   describe :country_code do
-    before :all do
+    around do |t|
+      old = I18nData.data_provider
       I18nData.data_provider = I18nData::FileDataProvider
+      t.call
+    ensure
+      I18nData.data_provider = old
     end
 
     it "recognises a countries name" do
@@ -187,7 +191,7 @@ def blank_keys_or_values(hash)
     end
 
     it "returns nil when it cannot recognise" do
-      I18nData.country_code('XY').should eq nil
+      I18nData.country_code('XY').should be_nil
     end
 
     it "can find languages that are not in english list" do
@@ -218,7 +222,7 @@ def blank_keys_or_values(hash)
     end
 
     it "returns nil when it cannot recognise" do
-      I18nData.language_code('XY').should eq nil
+      I18nData.language_code('XY').should be_nil
     end
   end
 
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 2dbc20d..6a7107f 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 $LOAD_PATH << 'lib'
 require 'i18n_data'