Add new Minitest/AssertPredicate and Minitest/RefutePredicate cops

changelog/new_add_new_minitest_assert_predicate_refute_predicate_cops.md

@@ -0,0 +1 @@
+* [#161](https://github.com/rubocop/rubocop-minitest/pull/161): Add new `Minitest/AssertPredicate` and `Minitest/RefutePredicate` cops. ([@koic][])

config/default.yml

@@ -81,6 +81,12 @@ Minitest/AssertRespondTo:
   Enabled: true
   VersionAdded: '0.3'
 
+Minitest/AssertPredicate:
+  Description: 'This cop enforces the test to use `assert_predicate` instead of using `assert(obj.a_predicate_method?)`.'
+  StyleGuide: 'https://minitest.rubystyle.guide/#assert-predicate'
+  Enabled: pending
+  VersionAdded: '<<next>>'
+
 Minitest/AssertSilent:
   Description: "This cop enforces the test to use `assert_silent { ... }` instead of using `assert_output('', '') { ... }`."
   StyleGuide: 'https://github.com/rubocop/minitest-style-guide#assert-silent'
@@ -194,6 +200,12 @@ Minitest/RefutePathExists:
   Enabled: 'pending'
   VersionAdded: '0.10'
 
+Minitest/RefutePredicate:
+  Description: 'This cop enforces the test to use `refute_predicate` instead of using `refute(obj.a_predicate_method?)`.'
+  StyleGuide: 'https://minitest.rubystyle.guide/#refute-predicate'
+  Enabled: pending
+  VersionAdded: '<<next>>'
+
 Minitest/RefuteRespondTo:
   Description: 'This cop enforces the test to use `refute_respond_to(object, :do_something)` over `refute(object.respond_to?(:do_something))`.'
   StyleGuide: 'https://minitest.rubystyle.guide#refute-respond-to'

lib/rubocop/cop/minitest/assert_predicate.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Minitest
+      # This cop enforces the test to use `assert_predicate`
+      # instead of using `assert(obj.a_predicate_method?)`.
+      #
+      # @example
+      #   # bad
+      #   assert(obj.one?)
+      #   assert(obj.one?, 'message')
+      #
+      #   # good
+      #   assert_predicate(obj, :one?)
+      #   assert_predicate(obj, :one?, 'message')
+      #
+      class AssertPredicate < Base
+        include ArgumentRangeHelper
+        include PredicateAssertionHandleable
+        extend AutoCorrector
+
+        MSG = 'Prefer using `assert_predicate(%<new_arguments>s)`.'
+        RESTRICT_ON_SEND = %i[assert].freeze
+
+        private
+
+        def assertion_type
+          'assert'
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/minitest/refute_predicate.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Minitest
+      # This cop enforces the test to use `refute_predicate`
+      # instead of using `refute(obj.a_predicate_method?)`.
+      #
+      # @example
+      #   # bad
+      #   refute(obj.one?)
+      #   refute(obj.one?, 'message')
+      #
+      #   # good
+      #   refute_predicate(obj, :one?)
+      #   refute_predicate(obj, :one?, 'message')
+      #
+      class RefutePredicate < Base
+        include ArgumentRangeHelper
+        include PredicateAssertionHandleable
+        extend AutoCorrector
+
+        MSG = 'Prefer using `refute_predicate(%<new_arguments>s)`.'
+        RESTRICT_ON_SEND = %i[refute].freeze
+
+        private
+
+        def assertion_type
+          'refute'
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/minitest_cops.rb

@@ -5,10 +5,12 @@
 require_relative 'mixin/minitest_cop_rule'
 require_relative 'mixin/minitest_exploration_helpers'
 require_relative 'mixin/nil_assertion_handleable'
+require_relative 'mixin/predicate_assertion_handleable'
 require_relative 'minitest/assert_empty'
 require_relative 'minitest/assert_empty_literal'
 require_relative 'minitest/assert_equal'
 require_relative 'minitest/assert_in_delta'
+require_relative 'minitest/assert_predicate'
 require_relative 'minitest/assert_with_expected_argument'
 require_relative 'minitest/assertion_in_lifecycle_hook'
 require_relative 'minitest/assert_kind_of'
@@ -35,6 +37,7 @@
 require_relative 'minitest/refute_match'
 require_relative 'minitest/refute_instance_of'
 require_relative 'minitest/refute_path_exists'
+require_relative 'minitest/refute_predicate'
 require_relative 'minitest/refute_respond_to'
 require_relative 'minitest/test_method_name'
 require_relative 'minitest/unreachable_assertion'

lib/rubocop/cop/mixin/predicate_assertion_handleable.rb

@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Minitest
+      # Common functionality for `Minitest/AssertPredicate` and `Minitest/RefutePredicate` cops.
+      module PredicateAssertionHandleable
+        MSG = 'Prefer using `%<assertion_type>s_predicate(%<new_arguments>s)`.'
+        RESTRICT_ON_SEND = %i[assert].freeze
+
+        def on_send(node)
+          return unless (arguments = peel_redundant_parentheses_from(node.arguments))
+          return unless arguments.first.respond_to?(:predicate_method?) && arguments.first.predicate_method?
+          return unless arguments.first.arguments.count.zero?
+
+          add_offense(node, message: offense_message(arguments)) do |corrector|
+            autocorrect(corrector, node, arguments)
+          end
+        end
+
+        def autocorrect(corrector, node, arguments)
+          corrector.replace(node.loc.selector, "#{assertion_type}_predicate")
+
+          new_arguments = new_arguments(arguments).join(', ')
+
+          corrector.replace(first_argument_range(node), new_arguments)
+        end
+
+        private
+
+        def peel_redundant_parentheses_from(arguments)
+          return arguments unless arguments.first&.begin_type?
+
+          peel_redundant_parentheses_from(arguments.first.children)
+        end
+
+        def offense_message(arguments)
+          message_argument = arguments.last if arguments.first != arguments.last
+
+          new_arguments = [
+            new_arguments(arguments),
+            message_argument&.source
+          ].flatten.compact.join(', ')
+
+          format(MSG, assertion_type: assertion_type, new_arguments: new_arguments)
+        end
+
+        def new_arguments(arguments)
+          receiver = correct_receiver(arguments.first.receiver)
+          method_name = arguments.first.method_name
+
+          [receiver, ":#{method_name}"]
+        end
+
+        def correct_receiver(receiver)
+          receiver ? receiver.source : 'self'
+        end
+      end
+    end
+  end
+end

test/rubocop/cop/minitest/assert_predicate_test.rb

@@ -0,0 +1,145 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class AssertPredicateTest < Minitest::Test
+  def test_registers_offense_when_using_assert_with_predicate_method
+    assert_offense(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert(obj.one?)
+          ^^^^^^^^^^^^^^^^ Prefer using `assert_predicate(obj, :one?)`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert_predicate(obj, :one?)
+        end
+      end
+    RUBY
+  end
+
+  def test_registers_offense_when_using_assert_with_predicate_method_and_message
+    assert_offense(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert(obj.one?, 'message')
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `assert_predicate(obj, :one?, 'message')`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert_predicate(obj, :one?, 'message')
+        end
+      end
+    RUBY
+  end
+
+  def test_registers_offense_when_using_assert_with_predicate_method_and_heredoc_message
+    assert_offense(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert(obj.one?, <<~MESSAGE)
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer using `assert_predicate(obj, :one?, <<~MESSAGE)`.
+            message
+          MESSAGE
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert_predicate(obj, :one?, <<~MESSAGE)
+            message
+          MESSAGE
+        end
+      end
+    RUBY
+  end
+
+  def test_registers_offense_when_using_assert_with_predicate_method_in_redundant_parentheses
+    assert_offense(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert((obj.one?))
+          ^^^^^^^^^^^^^^^^^^ Prefer using `assert_predicate(obj, :one?)`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert_predicate(obj, :one?)
+        end
+      end
+    RUBY
+  end
+
+  def test_registers_offense_when_using_assert_with_receiver_omitted_predicate_method
+    assert_offense(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert(one?)
+          ^^^^^^^^^^^^ Prefer using `assert_predicate(self, :one?)`.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert_predicate(self, :one?)
+        end
+      end
+    RUBY
+  end
+
+  def test_does_not_register_offense_when_using_assert_predicate_method
+    assert_no_offenses(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert_predicate(obj, :one?)
+        end
+      end
+    RUBY
+  end
+
+  def test_does_not_registers_offense_when_using_assert_with_non_predicate_method
+    assert_no_offenses(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert(obj.do_something)
+        end
+      end
+    RUBY
+  end
+
+  def test_does_not_registers_offense_when_using_assert_with_local_variable
+    assert_no_offenses(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          obj = create_obj
+          assert(obj)
+        end
+      end
+    RUBY
+  end
+
+  def test_does_not_register_offense_when_using_assert_with_predicate_method_and_arguments
+    assert_no_offenses(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+          assert(obj.foo?(arg))
+        end
+      end
+    RUBY
+  end
+end