Fix an error for Minitest/MultipleAssertions when using for-style l…

…oops

They produce an assign node, but the value is part of the parent for node

changelog/fix_error_multiple_assertions.md

@@ -0,0 +1 @@
+* [#317](https://github.com/rubocop/rubocop-minitest/pull/317): Fix an error for `Minitest/MultipleAssertions` when using for-style loops. ([@earlopain][])

lib/rubocop/cop/minitest/multiple_assertions.rb

@@ -75,7 +75,11 @@ def assertions_count_based_on_type(node)
         end
 
         def assertions_count_in_assignment(node)
-          return assertions_count_based_on_type(node.expression) unless node.masgn_type?
+          unless node.masgn_type?
+            return 0 unless node.expression # for-style loop
+
+            return assertions_count_based_on_type(node.expression)
+          end
 
           rhs = node.children.last
 

test/rubocop/cop/minitest/multiple_assertions_test.rb

@@ -616,6 +616,20 @@ class FooTest < ActiveSupport::TestCase
     RUBY
   end
 
+  def test_registers_offense_when_for_style_loop
+    assert_offense(<<~RUBY)
+      class FooTest < Minitest::Test
+        def test_asserts_twice
+        ^^^^^^^^^^^^^^^^^^^^^^ Test case has too many assertions [2/1].
+          assert_equal(foo, bar)
+          for baz in [1, 2]
+            assert_equal(baz, 1)
+          end
+        end
+      end
+    RUBY
+  end
+
   def test_registers_offense_when_complex_multiple_assignment_structure_and_multiple_assertions
     skip 'FIXME: The shared `@cop` instance variable causes flaky tests due to state changes.'