[Fix #332] Fix false positives for Minitest/NoAssertions

changelog/fix_false_positives_for_minitest_no_assertion_test.md

@@ -0,0 +1 @@
+* [#332](https://github.com/rubocop/rubocop-minitest/issues/332): Fix false positives for `Minitest/NoAssertions` when using matcher methods. ([@koic][])

lib/rubocop/cop/minitest/global_expectations.rb

@@ -87,20 +87,10 @@ class GlobalExpectations < Base
 
         MSG = 'Use `%<preferred>s` instead.'
 
-        VALUE_MATCHERS = %i[
-          must_be_empty must_equal must_be_close_to must_be_within_delta
-          must_be_within_epsilon must_include must_be_instance_of must_be_kind_of
-          must_match must_be_nil must_be must_respond_to must_be_same_as
-          path_must_exist path_wont_exist wont_be_empty wont_equal wont_be_close_to
-          wont_be_within_delta wont_be_within_epsilon wont_include wont_be_instance_of
-          wont_be_kind_of wont_match wont_be_nil wont_be wont_respond_to wont_be_same_as
-        ].freeze
-
-        BLOCK_MATCHERS = %i[
-          must_output must_pattern_match must_raise must_be_silent must_throw wont_pattern_match
-        ].freeze
-
-        RESTRICT_ON_SEND = VALUE_MATCHERS + BLOCK_MATCHERS
+        VALUE_MATCHERS = MinitestExplorationHelpers::VALUE_MATCHERS
+        BLOCK_MATCHERS = MinitestExplorationHelpers::BLOCK_MATCHERS
+
+        RESTRICT_ON_SEND = MinitestExplorationHelpers::MATCHER_METHODS
 
         # There are aliases for the `_` method - `expect` and `value`
         DSL_METHODS = %i[_ expect value].freeze

lib/rubocop/cop/minitest/no_assertions.rb

@@ -5,6 +5,8 @@ module Cop
     module Minitest
       # Checks if test cases contain any assertion calls.
       #
+      # Matchers such as `must_equal` and `wont_match` are also treated as assertion methods.
+      #
       # @example
       #   # bad
       #   class FooTest < Minitest::Test
@@ -19,6 +21,23 @@ module Minitest
       #     end
       #   end
       #
+      #   # bad
+      #   class FooTest < ActiveSupport::TestCase
+      #     describe 'foo' do
+      #       it 'test equal' do
+      #       end
+      #     end
+      #   end
+      #
+      #   # good
+      #   class FooTest < ActiveSupport::TestCase
+      #     describe 'foo' do
+      #       it 'test equal' do
+      #         musts.must_equal expected_musts
+      #       end
+      #     end
+      #   end
+      #
       class NoAssertions < Base
         include MinitestExplorationHelpers
 

lib/rubocop/cop/mixin/minitest_exploration_helpers.rb

@@ -10,7 +10,22 @@ module MinitestExplorationHelpers
       include DefNode
       extend NodePattern::Macros
 
-      ASSERTION_PREFIXES = %w[assert refute].freeze
+      VALUE_MATCHERS = %i[
+        must_be_empty must_equal must_be_close_to must_be_within_delta
+        must_be_within_epsilon must_include must_be_instance_of must_be_kind_of
+        must_match must_be_nil must_be must_respond_to must_be_same_as
+        path_must_exist path_wont_exist wont_be_empty wont_equal wont_be_close_to
+        wont_be_within_delta wont_be_within_epsilon wont_include wont_be_instance_of
+        wont_be_kind_of wont_match wont_be_nil wont_be wont_respond_to wont_be_same_as
+      ].freeze
+
+      BLOCK_MATCHERS = %i[
+        must_output must_pattern_match must_raise must_be_silent must_throw wont_pattern_match
+      ].freeze
+
+      MATCHER_METHODS = VALUE_MATCHERS + BLOCK_MATCHERS
+
+      ASSERTION_PREFIXES = %i[assert refute].freeze
 
       LIFECYCLE_HOOK_METHODS_IN_ORDER = %i[
         before_setup
@@ -99,17 +114,18 @@ def assertions_count(node)
         end
       end
 
+      # rubocop:disable Metrics/CyclomaticComplexity
       def assertion_method?(node)
         return false unless node
         return assertion_method?(node.expression) if node.assignment? && node.respond_to?(:expression)
         return false unless node.type?(:send, :any_block)
 
-        ASSERTION_PREFIXES.any? do |prefix|
-          method_name = node.method_name
+        method_name = node.method_name
+        assertion_method = ASSERTION_PREFIXES.any? { |prefix| method_name.start_with?(prefix.to_s) }
 
-          method_name.start_with?(prefix) || node.method?(:flunk)
-        end
+        assertion_method || node.method?(:flunk) || MATCHER_METHODS.include?(method_name)
       end
+      # rubocop:enable Metrics/CyclomaticComplexity
 
       def lifecycle_hook_method?(node)
         node.def_type? && LIFECYCLE_HOOK_METHODS.include?(node.method_name)

test/rubocop/cop/minitest/no_assertions_test.rb

@@ -78,6 +78,30 @@ def test_the_truth
     RUBY
   end
 
+  def test_register_no_offense_if_test_has_must_be_empty_assertion
+    assert_no_offenses(<<~RUBY)
+      class FooTest < Minitest::Test
+        describe 'foo' do
+          it 'must have good data' do
+            _(invalid_recs).must_be_empty ->{ do_something }
+          end
+        end
+      end
+    RUBY
+  end
+
+  def test_register_no_offense_if_test_has_must_include_assertion
+    assert_no_offenses(<<~RUBY)
+      class FooTest < Minitest::Test
+        describe 'foo' do
+          it 'must include [false, true]' do
+            value([false, true]).must_include value
+          end
+        end
+      end
+    RUBY
+  end
+
   def test_register_no_offense_for_unrelated_methods
     assert_no_offenses(<<~RUBY)
       class FooTest < Minitest::Test