Merge pull request #11 from tejasbubane/refute-nil-cop

Add new cop `Minitest/RefuteNil`

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## master (unreleased)
 
+### New features
+
+* [#11](https://github.com/rubocop-hq/rubocop-minitest/pull/11): Add new `Minitest/RefuteNil` cop. ([@tejasbubane ][])
+
 ## 0.1.0 (2019-09-01)
 
 ### New features
@@ -9,3 +13,4 @@
 
 [@koic]: https://github.com/koic
 [@duduribeiro]: https://github.com/duduribeiro
+[@tejasbubane]: https://github.com/tejasbubane

config/default.yml

@@ -7,3 +7,9 @@ Minitest/AssertNil:
   StyleGuide: 'https://github.com/rubocop-hq/minitest-style-guide#assert-nil'
   Enabled: true
   VersionAdded: '0.1'
+
+Minitest/RefuteNil:
+  Description: 'Check if your test uses `refute_nil` instead of `refute_equal(nil, something)`.'
+  StyleGuide: 'https://github.com/rubocop-hq/minitest-style-guide#refute-nil'
+  Enabled: true
+  VersionAdded: '0.1.1'

lib/rubocop/cop/minitest/refute_nil.rb

@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Minitest
+      # Check if your test uses `refute_nil` instead of `refute_equal(nil, something)`.
+      #
+      # @example
+      #   # bad
+      #   refute_equal(nil, actual)
+      #   refute_equal(nil, actual, 'the message')
+      #
+      #   # good
+      #   refute_nil(actual)
+      #   refute_nil(actual, 'the message')
+      #
+      class RefuteNil < Cop
+        MSG = 'Prefer using `refute_nil(%<arguments>s)` over ' \
+              '`refute_equal(nil, %<arguments>s)`.'
+
+        def_node_matcher :refute_equal_with_nil, <<~PATTERN
+          (send nil? :refute_equal nil $_ $...)
+        PATTERN
+
+        def on_send(node)
+          refute_equal_with_nil(node) do |actual, message|
+            message = message.first
+
+            arguments = [actual.source, message&.source].compact.join(', ')
+
+            add_offense(node, message: format(MSG, arguments: arguments))
+          end
+        end
+
+        def autocorrect(node)
+          lambda do |corrector|
+            arguments = node.arguments.reject(&:nil_type?)
+            replacement = arguments.map(&:source).join(', ')
+            corrector.replace(node.loc.expression, "refute_nil(#{replacement})")
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/minitest_cops.rb

@@ -1,3 +1,4 @@
 # frozen_string_literal: true
 
 require_relative 'minitest/assert_nil'
+require_relative 'minitest/refute_nil'

manual/cops.md

@@ -2,5 +2,6 @@
 #### Department [Minitest](cops_minitest.md)
 
 * [Minitest/AssertNil](cops_minitest.md#minitestassertnil)
+* [Minitest/RefuteNil](cops_minitest.md#minitestrefutenil)
 
 <!-- END_COP_LIST -->

manual/cops_minitest.md

@@ -23,3 +23,27 @@ assert_nil(actual, 'the message')
 ### References
 
 * [https://github.com/rubocop-hq/minitest-style-guide#assert-nil](https://github.com/rubocop-hq/minitest-style-guide#assert-nil)
+
+## Minitest/RefuteNil
+
+Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
+--- | --- | --- | --- | ---
+Enabled | Yes | Yes  | 0.1.1 | -
+
+Check if your test uses `refute_nil` instead of `refute_equal(nil, something)`.
+
+### Examples
+
+```ruby
+# bad
+refute_equal(nil, actual)
+refute_equal(nil, actual, 'the message')
+
+# good
+refute_nil(actual)
+refute_nil(actual, 'the message')
+```
+
+### References
+
+* [https://github.com/rubocop-hq/minitest-style-guide#refute-nil](https://github.com/rubocop-hq/minitest-style-guide#refute-nil)

test/rubocop/cop/minitest/refute_nil_test.rb

@@ -0,0 +1,120 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class RefuteNilTest < Minitest::Test
+  def setup
+    @cop = RuboCop::Cop::Minitest::RefuteNil.new
+  end
+
+  def test_adds_offense_for_use_of_refute_equal_nil
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute_equal(nil, somestuff)
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `refute_nil(somestuff)` over `refute_equal(nil, somestuff)`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute_nil(somestuff)
+        end
+      end
+    RUBY
+  end
+
+  def test_adds_offense_for_use_of_refute_equal_nil_with_message
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute_equal(nil, somestuff, 'the message')
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `refute_nil(somestuff, 'the message')` over `refute_equal(nil, somestuff, 'the message')`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute_nil(somestuff, 'the message')
+        end
+      end
+    RUBY
+  end
+
+  def test_adds_offense_for_use_of_refute_equal_with_a_method_call
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute_equal(nil, obj.do_something, 'the message')
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `refute_nil(obj.do_something, 'the message')` over `refute_equal(nil, obj.do_something, 'the message')`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute_nil(obj.do_something, 'the message')
+        end
+      end
+    RUBY
+  end
+
+  def test_adds_offense_for_use_of_refute_equal_with_a_string_variable_in_message
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          message = 'the message'
+          refute_equal(nil, somestuff, message)
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `refute_nil(somestuff, message)` over `refute_equal(nil, somestuff, message)`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          message = 'the message'
+          refute_nil(somestuff, message)
+        end
+      end
+    RUBY
+  end
+
+  def test_adds_offense_for_use_of_refute_equal_with_a_constant_in_message
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        MESSAGE = 'the message'
+
+        def test_do_something
+          refute_equal(nil, somestuff, MESSAGE)
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `refute_nil(somestuff, MESSAGE)` over `refute_equal(nil, somestuff, MESSAGE)`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        MESSAGE = 'the message'
+
+        def test_do_something
+          refute_nil(somestuff, MESSAGE)
+        end
+      end
+    RUBY
+  end
+
+  def test_does_not_offend_if_using_refute_nil
+    assert_no_offenses(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          refute_nil(somestuff)
+        end
+      end
+    RUBY
+  end
+end