[Fix #189] Fix a false positive for `Minitest/EmptyLineBeforeAssertio…

…nMethods`

Fixes #189 and #194.

This PR fixes a false negative for `Minitest/EmptyLineBeforeAssertionMethods`
when using assertion method used in block before assertion method.

changelog/fix_false_positive_for_minitest_empty_line_before_assertion_methods.md

@@ -0,0 +1 @@
+* [#189](https://github.com/rubocop/rubocop-minitest/issues/189): Fix a false negative for `Minitest/EmptyLineBeforeAssertionMethods` when using assertion method used in block before assertion method. ([@koic][])

lib/rubocop/cop/minitest/empty_line_before_assertion_methods.rb

@@ -23,26 +23,28 @@ class EmptyLineBeforeAssertionMethods < Base
 
         MSG = 'Add empty line before assertion.'
 
+        # rubocop:disable Metrics/CyclomaticComplexity
         def on_send(node)
           return unless (assertion_method = assertion_method(node))
           return unless (previous_line_node = assertion_method.left_sibling)
           return if node.parent.resbody_type?
           return if accept_previous_line?(previous_line_node, assertion_method)
 
           previous_line_node = previous_line_node.arguments.last if use_heredoc_argument?(previous_line_node)
+          return if use_assertion_method_at_last_of_block?(previous_line_node)
           return unless no_empty_line?(previous_line_node, assertion_method)
 
           register_offense(assertion_method, previous_line_node)
         end
+        # rubocop:enable Metrics/CyclomaticComplexity
 
         private
 
         def assertion_method(node)
-          if assertion_method?(node)
-            node
-          elsif node.parent&.block_type? && assertion_method?(node.parent.body)
-            node.parent
-          end
+          return node if assertion_method?(node)
+          return unless (parent = node.parent)
+
+          node.parent if parent.block_type? && parent.body && assertion_method?(parent.body)
         end
 
         def accept_previous_line?(previous_line_node, node)
@@ -56,6 +58,16 @@ def use_heredoc_argument?(node)
           node.respond_to?(:arguments) && heredoc?(node.arguments.last)
         end
 
+        def use_assertion_method_at_last_of_block?(node)
+          return false if !node.block_type? || !node.body
+
+          if node.body.begin_type?
+            assertion_method?(node.body.children.last)
+          else
+            assertion_method?(node.body)
+          end
+        end
+
         def heredoc?(last_argument)
           last_argument.respond_to?(:heredoc?) && last_argument.heredoc?
         end

test/rubocop/cop/minitest/empty_line_before_assertion_methods_test.rb

@@ -167,6 +167,70 @@ def test_do_something
     RUBY
   end
 
+  def test_registers_offense_when_using_non_assertion_method_used_in_single_line_block_before_assertion_method
+    assert_offense(<<~RUBY)
+      def test_do_something
+        set.each { |thing| do_something(thing) }
+        assert_equal 'This is really bad', error.message
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Add empty line before assertion.
+      end
+    RUBY
+
+    assert_correction(<<~RUBY)
+      def test_do_something
+        set.each { |thing| do_something(thing) }
+
+        assert_equal 'This is really bad', error.message
+      end
+    RUBY
+  end
+
+  def test_registers_offense_when_using_non_assertion_method_used_in_multi_line_block_before_assertion_method
+    assert_offense(<<~RUBY)
+      def test_do_something
+        set.each do |thing|
+          refute_nil(thing)
+
+          do_something(thing)
+        end
+        assert_equal 'This is really bad', error.message
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Add empty line before assertion.
+      end
+    RUBY
+
+    assert_correction(<<~RUBY)
+      def test_do_something
+        set.each do |thing|
+          refute_nil(thing)
+
+          do_something(thing)
+        end
+
+        assert_equal 'This is really bad', error.message
+      end
+    RUBY
+  end
+
+  def test_registers_offense_when_using_empty_block_before_assertion_method
+    assert_offense(<<~RUBY)
+      def test_do_something
+        set.each do |thing|
+        end
+        assert_equal 'This is really bad', error.message
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Add empty line before assertion.
+      end
+    RUBY
+
+    assert_correction(<<~RUBY)
+      def test_do_something
+        set.each do |thing|
+        end
+
+        assert_equal 'This is really bad', error.message
+      end
+    RUBY
+  end
+
   def test_registers_offense_when_using_statement_before_assertion_method_used_in_rescue
     assert_offense(<<~'RUBY')
       def test_do_something
@@ -258,7 +322,7 @@ def test_do_something
     RUBY
   end
 
-  def test_registers_offense_when_using_assertion_method_before_assertion_method_used_in_block
+  def test_does_not_register_offense_when_using_assertion_method_before_assertion_method_used_in_block
     assert_no_offenses(<<~RUBY)
       def test_do_something
         set = Set.new([1,2,3])
@@ -282,6 +346,28 @@ def test_do_something
     RUBY
   end
 
+  def test_does_not_register_offense_when_using_assertion_method_used_in_single_line_block_before_assertion_method
+    assert_no_offenses(<<~RUBY)
+      def test_do_something
+        set.each { |thing| refute_nil(thing) }
+        assert_equal 'This is really bad', error.message
+      end
+    RUBY
+  end
+
+  def test_does_not_register_offense_when_using_assertion_method_used_in_multi_line_block_before_assertion_method
+    assert_no_offenses(<<~RUBY)
+      def test_do_something
+        set.each do |thing|
+          do_something
+
+          refute_nil(thing)
+        end
+        assert_equal 'This is really bad', error.message
+      end
+    RUBY
+  end
+
   def test_does_not_register_offense_when_using_rescue_before_assertion_method
     assert_no_offenses(<<~'RUBY')
       def test_do_something