Add new Minitest/TestCaseName cop

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 * [#92](https://github.com/rubocop-hq/rubocop-minitest/pull/92): Add new `Minitest/LiteralAsActualArgument` cop. ([@fatkodima][])
 * [#91](https://github.com/rubocop-hq/rubocop-minitest/pull/91): Add new `Minitest/AssertInDelta` and `Minitest/RefuteInDelta` cops. ([@fatkodima][])
+* [#89](https://github.com/rubocop-hq/rubocop-minitest/pull/89): Add new `Minitest/TestMethodName` cop. ([@fatkodima][])
 * [#83](https://github.com/rubocop-hq/rubocop-minitest/pull/83): New cops `AssertPathExists` and `RefutePathExists` check for use of `assert_path_exists`/`refute_path_exists` instead of `assert(File.exist?(path))`/`refute(File.exist?(path))`. ([@fatkodima][])
 * [#88](https://github.com/rubocop-hq/rubocop-minitest/pull/88): Add new `Minitest/MultipleAssertions` cop. ([@fatkodima][])
 * [#87](https://github.com/rubocop-hq/rubocop-minitest/pull/87): Add new `Minitest/AssertSilent` cop. ([@fatkodima][])

config/default.yml

@@ -167,6 +167,11 @@ Minitest/RefuteRespondTo:
   Enabled: true
   VersionAdded: '0.4'
 
+Minitest/TestMethodName:
+  Description: 'This cop enforces that test method names start with `test_` prefix.'
+  Enabled: 'pending'
+  VersionAdded: '0.10'
+
 Minitest/UnspecifiedException:
   Description: 'This cop checks for a specified error in `assert_raises`.'
   StyleGuide: 'https://minitest.rubystyle.guide#unspecified-exception'

docs/modules/ROOT/pages/cops.adoc

@@ -29,6 +29,7 @@
 * xref:cops_minitest.adoc#minitestrefutenil[Minitest/RefuteNil]
 * xref:cops_minitest.adoc#minitestrefutepathexists[Minitest/RefutePathExists]
 * xref:cops_minitest.adoc#minitestrefuterespondto[Minitest/RefuteRespondTo]
+* xref:cops_minitest.adoc#minitesttestmethodname[Minitest/TestMethodName]
 * xref:cops_minitest.adoc#minitestunspecifiedexception[Minitest/UnspecifiedException]
 
 // END_COP_LIST

docs/modules/ROOT/pages/cops_minitest.adoc

@@ -884,6 +884,39 @@ refute_respond_to(self, :do_something)
 
 * https://minitest.rubystyle.guide#refute-respond-to
 
+== Minitest/TestMethodName
+
+|===
+| Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
+
+| Pending
+| Yes
+| Yes
+| 0.10
+| -
+|===
+
+This cop enforces that test method names start with `test_` prefix.
+
+=== Examples
+
+[source,ruby]
+----
+# bad
+class FooTest < Minitest::Test
+  def does_something
+    assert_equal 42, do_something
+  end
+end
+
+# good
+class FooTest < Minitest::Test
+  def test_does_something
+    assert_equal 42, do_something
+  end
+end
+----
+
 == Minitest/UnspecifiedException
 
 |===

lib/rubocop/cop/minitest/test_method_name.rb

@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Minitest
+      # This cop enforces that test method names start with `test_` prefix.
+      #
+      # @example
+      #   # bad
+      #   class FooTest < Minitest::Test
+      #     def does_something
+      #       assert_equal 42, do_something
+      #     end
+      #   end
+      #
+      #   # good
+      #   class FooTest < Minitest::Test
+      #     def test_does_something
+      #       assert_equal 42, do_something
+      #     end
+      #   end
+      #
+      class TestMethodName < Cop
+        include MinitestExplorationHelpers
+        include DefNode
+
+        MSG = 'Test method name should start with `test_` prefix.'
+
+        def on_class(class_node)
+          return unless test_class?(class_node)
+
+          class_elements(class_node).each do |node|
+            add_offense(node, location: :name) if offense?(node)
+          end
+        end
+
+        def autocorrect(node)
+          lambda do |corrector|
+            corrector.replace(node.loc.name, "test_#{node.method_name}")
+          end
+        end
+
+        private
+
+        def class_elements(class_node)
+          class_def = class_node.body
+          return [] unless class_def
+
+          if class_def.def_type?
+            [class_def]
+          else
+            class_def.each_child_node(:def).to_a
+          end
+        end
+
+        def offense?(node)
+          public?(node) && !test_method_name?(node) && !lifecycle_hook_method?(node)
+        end
+
+        def public?(node)
+          !non_public?(node)
+        end
+
+        def test_method_name?(node)
+          node.method_name.to_s.start_with?('test_')
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/minitest_cops.rb

@@ -31,4 +31,5 @@
 require_relative 'minitest/refute_instance_of'
 require_relative 'minitest/refute_path_exists'
 require_relative 'minitest/refute_respond_to'
+require_relative 'minitest/test_method_name'
 require_relative 'minitest/unspecified_exception'

lib/rubocop/cop/mixin/minitest_exploration_helpers.rb

@@ -47,6 +47,15 @@ module MinitestExplorationHelpers
         refute_same
       ].to_set.freeze
 
+      LIFECYCLE_HOOK_METHODS = %i[
+        before_setup
+        setup
+        after_setup
+        before_teardown
+        teardown
+        after_teardown
+      ].to_set.freeze
+
       private
 
       def test_class?(class_node)
@@ -70,6 +79,10 @@ def test_cases(class_node)
       def assertion?(node)
         node.send_type? && ASSERTIONS.include?(node.method_name)
       end
+
+      def lifecycle_hook_method?(node)
+        node.def_type? && LIFECYCLE_HOOK_METHODS.include?(node.method_name)
+      end
     end
   end
 end

test/rubocop/cop/minitest/refute_empty_test.rb

@@ -85,7 +85,7 @@ def test_do_something
     RUBY
   end
 
-  def refute_empty_method
+  def test_refute_empty_method
     assert_no_offenses(<<~RUBY)
       class FooTest < Minitest::Test
         def test_do_something

test/rubocop/cop/minitest/refute_instance_of_test.rb

@@ -85,7 +85,7 @@ def test_do_something
     RUBY
   end
 
-  def refute_instance_of_method
+  def test_refute_instance_of_method
     assert_no_offenses(<<~RUBY)
       class FooTest < Minitest::Test
         def test_do_something

test/rubocop/cop/minitest/test_method_name_test.rb

@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class TestMethodNameTest < Minitest::Test
+  def test_registers_offense_when_test_method_without_prefix
+    assert_offense(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+        end
+
+        def do_something_else
+            ^^^^^^^^^^^^^^^^^ Test method name should start with `test_` prefix.
+        end
+      end
+    RUBY
+
+    assert_correction(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_do_something
+        end
+
+        def test_do_something_else
+        end
+      end
+    RUBY
+  end
+
+  def test_checks_only_test_classes
+    assert_no_offenses(<<~RUBY)
+      class FooTest
+        def do_something
+        end
+      end
+    RUBY
+  end
+
+  def test_does_not_register_offense_when_hook_method
+    assert_no_offenses(<<~RUBY)
+      class FooTest < Minitest::Test
+        def setup
+        end
+      end
+    RUBY
+  end
+
+  def test_does_not_register_offense_when_non_public_method
+    assert_no_offenses(<<~RUBY)
+      class FooTest < Minitest::Test
+        private
+
+        def do_something
+        end
+      end
+    RUBY
+  end
+end