anchor.diff:        expect(instance == instance, true);
       });
   
  +    test('should return correct hashCode', () {
  +      final instance = EmptyEquatable();
  +      expect(instance.hashCode, instance.runtimeType.hashCode);
  +    });
  +
       test('should return true when instances are different', () {
         final instanceA = EmptyEquatable();
         final instanceB = EmptyEquatable();
  
positive.code:     test('should return true when instance is the same', () {
        final instance = SimpleEquatable('simple');
        expect(instance == instance, true);
      });
  
      test('should return true when instances are different', () {
  
negative.code:         hairColor: Color.black,
        );
        expect(instance == instance, true);
      });
  
      test('should return correct hashCode', () {
        final instance = ComplexEquatable(
          name: 'Joe',
          age: 40,
          hairColor: Color.black,
        );
        expect(
          instance.hashCode,
          instance.runtimeType.hashCode ^
              instance.name.hashCode ^
              instance.age.hashCode ^
              instance.hairColor.hashCode,
        );
      });
  
      test('should return true when instances are different', () {
  