Add cop to enfore refute_empty over refute(actual.empty?)

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### New features
+
+* [#20](https://github.com/rubocop-hq/rubocop-minitest/pull/20): Add new `Minitest/RefuteEmpty` cop. ([@abhaynikam][])
+
 ## 0.2.1 (2019-09-24)
 
 ### Bug fixes

config/default.yml

@@ -31,3 +31,9 @@ Minitest/RefuteNil:
   StyleGuide: 'https://github.com/rubocop-hq/minitest-style-guide#refute-nil'
   Enabled: true
   VersionAdded: '0.2'
+
+Minitest/RefuteEmpty:
+  Description: 'Check if your test uses `refute_empty` instead of `refute(actual.empty?)`.'
+  StyleGuide: 'https://github.com/rubocop-hq/minitest-style-guide#refute-empty'
+  Enabled: true
+  VersionAdded: '0.3'

lib/rubocop/cop/minitest/refute_empty.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Minitest
+      # Check if your test uses `refute_empty` instead of `refute(actual.empty?)`.
+      #
+      # @example
+      #   # bad
+      #   refute(actual.empty?)
+      #   refute(actual.empty?, 'the message')
+      #
+      #   # good
+      #   refute_empty(actual)
+      #   refute_empty(actual, 'the message')
+      #
+      class RefuteEmpty < Cop
+        MSG = 'Prefer using `refute_empty(%<arguments>s)` over ' \
+              '`refute(%<receiver>s)`.'
+
+        def_node_matcher :refute_with_empty, <<~PATTERN
+          (send nil? :refute $(send $_ :empty?) $...)
+        PATTERN
+
+        def on_send(node)
+          refute_with_empty(node) do |first_receiver_arg, actual, rest_receiver_arg|
+            message = rest_receiver_arg.first
+
+            arguments = [actual.source, message&.source].compact.join(', ')
+            receiver = [first_receiver_arg.source, message&.source].compact.join(', ')
+
+            offense_message = format(MSG, arguments: arguments, receiver: receiver)
+            add_offense(node, message: offense_message)
+          end
+        end
+
+        def autocorrect(node)
+          lambda do |corrector|
+            refute_with_empty(node) do |_first_receiver_arg, actual, rest_receiver_arg|
+              message = rest_receiver_arg.first
+
+              replacement = [actual.source, message&.source].compact.join(', ')
+              corrector.replace(node.loc.expression, "refute_empty(#{replacement})")
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/minitest_cops.rb

@@ -4,4 +4,5 @@
 require_relative 'minitest/assert_nil'
 require_relative 'minitest/assert_includes'
 require_relative 'minitest/assert_truthy'
+require_relative 'minitest/refute_empty'
 require_relative 'minitest/refute_nil'

manual/cops.md

@@ -5,6 +5,7 @@
 * [Minitest/AssertIncludes](cops_minitest.md#minitestassertincludes)
 * [Minitest/AssertNil](cops_minitest.md#minitestassertnil)
 * [Minitest/AssertTruthy](cops_minitest.md#minitestasserttruthy)
+* [Minitest/RefuteEmpty](cops_minitest.md#minitestrefuteempty)
 * [Minitest/RefuteNil](cops_minitest.md#minitestrefutenil)
 
 <!-- END_COP_LIST -->

manual/cops_minitest.md

@@ -98,6 +98,26 @@ assert(actual, 'the message')
 
 * [https://github.com/rubocop-hq/minitest-style-guide#assert-truthy](https://github.com/rubocop-hq/minitest-style-guide#assert-truthy)
 
+## Minitest/RefuteEmpty
+
+Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
+--- | --- | --- | --- | ---
+Enabled | Yes | Yes  | - | -
+
+Check if your test uses `refute_empty` instead of `refute(actual.empty?)`.
+
+### Examples
+
+```ruby
+# bad
+assert(actual.empty?)
+assert(actual.empty?, 'the message')
+
+# good
+refute_empty(actual)
+refute_empty(actual, 'the message')
+```
+
 ## Minitest/RefuteNil
 
 Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged

test/rubocop/cop/minitest/refute_empty_test.rb

@@ -0,0 +1,101 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class RefuteEmptyTest < Minitest::Test
+  def setup
+    @cop = RuboCop::Cop::Minitest::RefuteEmpty.new
+  end
+
+  def test_registers_offense_when_using_refute_with_empty
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute(somestuff.empty?)
+          ^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `refute_empty(somestuff)` over `refute(somestuff.empty?)`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute_empty(somestuff)
+        end
+      end
+    RUBY
+  end
+
+  def test_registers_offense_when_using_refute_with_empty_and_string_message
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute(somestuff.empty?, 'the message')
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `refute_empty(somestuff, 'the message')` over `refute(somestuff.empty?, 'the message')`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute_empty(somestuff, 'the message')
+        end
+      end
+    RUBY
+  end
+
+  def test_registers_offense_when_using_refute_with_empty_and_variable_message
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          message = 'the message'
+          refute(somestuff.empty?, message)
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `refute_empty(somestuff, message)` over `refute(somestuff.empty?, message)`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          message = 'the message'
+          refute_empty(somestuff, message)
+        end
+      end
+    RUBY
+  end
+
+  def test_registers_offense_when_using_refute_with_empty_and_constant_message
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        MESSAGE = 'the message'
+
+        def test_do_something
+          refute(somestuff.empty?, MESSAGE)
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `refute_empty(somestuff, MESSAGE)` over `refute(somestuff.empty?, MESSAGE)`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        MESSAGE = 'the message'
+
+        def test_do_something
+          refute_empty(somestuff, MESSAGE)
+        end
+      end
+    RUBY
+  end
+
+  def refute_empty_method
+    assert_no_offenses(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute_empty(somestuff)
+        end
+      end
+    RUBY
+  end
+end