Merge pull request #27 from duduribeiro/add_cop_to_enforce_assert_res…

…pond_to

Include a cop to enforce assert_respond_to

CHANGELOG.md

@@ -8,6 +8,7 @@
 * [#18](https://github.com/rubocop-hq/rubocop-minitest/pull/18): Add new `Minitest/RefuteFalse` cop. ([@duduribeiro][])
 * [#20](https://github.com/rubocop-hq/rubocop-minitest/pull/20): Add new `Minitest/RefuteEmpty` cop. ([@abhaynikam][])
 * [#21](https://github.com/rubocop-hq/rubocop-minitest/pull/21): Add new `Minitest/RefuteEqual` cop. ([@duduribeiro][])
+* [#27](https://github.com/rubocop-hq/rubocop-minitest/pull/27): Add new `Minitest/AssertRespondTo` cop. ([@duduribeiro][])
 
 ### Bug fixes
 

config/default.yml

@@ -20,6 +20,12 @@ Minitest/AssertIncludes:
   Enabled: true
   VersionAdded: '0.2'
 
+Minitest/AssertRespondTo:
+  Description: 'This cop enforces the test to use `assert_respond_to(object, :some_method)` over `assert(object.respond_to?(:some_method))`.'
+  StyleGuide: 'https://github.com/rubocop-hq/minitest-style-guide#assert-responds-to-method'
+  Enabled: true
+  VersionAdded: '0.3'
+
 Minitest/AssertTruthy:
   Description: 'This cop enforces the test to use `assert(actual)` instead of using `assert_equal(true, actual)`.'
   StyleGuide: 'https://github.com/rubocop-hq/minitest-style-guide#assert-truthy'

lib/rubocop/cop/minitest/assert_respond_to.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Minitest
+      # This cop enforces the use of `assert_respond_to(object, :some_method)`
+      # over `assert(object.respond_to?(:some_method))`.
+      #
+      # @example
+      #   # bad
+      #   assert(object.respond_to?(:some_method))
+      #   assert(object.respond_to?(:some_method), 'the message')
+      #
+      #   # good
+      #   assert_respond_to(object, :some_method)
+      #   assert_respond_to(object, :some_method, 'the message')
+      #
+      class AssertRespondTo < Cop
+        MSG = 'Prefer using `assert_respond_to(%<preferred>s)` over ' \
+              '`assert(%<over>s)`.'
+
+        def_node_matcher :assert_with_respond_to, <<~PATTERN
+          (send nil? :assert $(send $_ :respond_to? $_) $...)
+        PATTERN
+
+        def on_send(node)
+          assert_with_respond_to(node) do |over, object, method, rest_args|
+            custom_message = rest_args.first
+            preferred = [object, method, custom_message]
+                        .compact.map(&:source).join(', ')
+            over      = [over, custom_message].compact.map(&:source).join(', ')
+            message = format(MSG, preferred: preferred, over: over)
+            add_offense(node, message: message)
+          end
+        end
+
+        def autocorrect(node)
+          lambda do |corrector|
+            assert_with_respond_to(node) do |_, object, method, rest_args|
+              custom_message = rest_args.first
+              preferred = [object, method, custom_message]
+                          .compact.map(&:source).join(', ')
+              replacement = "assert_respond_to(#{preferred})"
+              corrector.replace(node.loc.expression, replacement)
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/minitest_cops.rb

@@ -3,6 +3,7 @@
 require_relative 'minitest/assert_empty'
 require_relative 'minitest/assert_nil'
 require_relative 'minitest/assert_includes'
+require_relative 'minitest/assert_respond_to'
 require_relative 'minitest/assert_truthy'
 require_relative 'minitest/refute_empty'
 require_relative 'minitest/refute_false'

manual/cops.md

@@ -4,6 +4,7 @@
 * [Minitest/AssertEmpty](cops_minitest.md#minitestassertempty)
 * [Minitest/AssertIncludes](cops_minitest.md#minitestassertincludes)
 * [Minitest/AssertNil](cops_minitest.md#minitestassertnil)
+* [Minitest/AssertRespondTo](cops_minitest.md#minitestassertrespondto)
 * [Minitest/AssertTruthy](cops_minitest.md#minitestasserttruthy)
 * [Minitest/RefuteEmpty](cops_minitest.md#minitestrefuteempty)
 * [Minitest/RefuteEqual](cops_minitest.md#minitestrefuteequal)

manual/cops_minitest.md

@@ -75,6 +75,31 @@ assert_nil(actual, 'the message')
 
 * [https://github.com/rubocop-hq/minitest-style-guide#assert-nil](https://github.com/rubocop-hq/minitest-style-guide#assert-nil)
 
+## Minitest/AssertRespondTo
+
+Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
+--- | --- | --- | --- | ---
+Enabled | Yes | Yes  | 0.3 | -
+
+This cop enforces the use of `assert_respond_to(object, :some_method)`
+over `assert(object.respond_to?(:some_method))`.
+
+### Examples
+
+```ruby
+# bad
+assert(object.respond_to?(:some_method))
+assert(object.respond_to?(:some_method), 'the message')
+
+# good
+assert_respond_to(object, :some_method)
+assert_respond_to(object, :some_method, 'the message')
+```
+
+### References
+
+* [https://github.com/rubocop-hq/minitest-style-guide#assert-responds-to-method](https://github.com/rubocop-hq/minitest-style-guide#assert-responds-to-method)
+
 ## Minitest/AssertTruthy
 
 Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged

test/rubocop/cop/minitest/assert_respond_to_test.rb

@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class AssertRespondToTest < Minitest::Test
+  def setup
+    @cop = RuboCop::Cop::Minitest::AssertRespondTo.new
+  end
+
+  def test_registers_offense_when_using_assert_calling_respond_to_method
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert(object.respond_to?(:some_method))
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `assert_respond_to(object, :some_method)` over `assert(object.respond_to?(:some_method))`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert_respond_to(object, :some_method)
+        end
+      end
+    RUBY
+  end
+
+  def test_registers_offense_when_using_assert_calling_respond_to_method_with_message
+    assert_offense(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert(object.respond_to?(:some_method), 'the message')
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `assert_respond_to(object, :some_method, 'the message')` over `assert(object.respond_to?(:some_method), 'the message')`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert_respond_to(object, :some_method, 'the message')
+        end
+      end
+    RUBY
+  end
+
+  def test_does_not_register_offense_when_using_assert_respond_to
+    assert_no_offenses(<<~RUBY, @cop)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert_respond_to('rubocop-minitest', :some_method)
+        end
+      end
+    RUBY
+  end
+end