anchor.diff:    set f(_) {}
   }
   ''');
  -    ClassElement element2 = findElement('A');
  +    ClassElement element2 = findElement.class_('A');
       assertThat(element2.getField('f')).isWrittenAt('f = 42', true);
     }
   
  
positive.code:   a[1] = 42;
  }
  ''');
      MethodElement readElement = findElement('[]');
      MethodElement writeElement = findElement('[]=');
      assertThat(readElement).isInvokedAt('[0]', true, length: 1);
      assertThat(writeElement).isInvokedAt('[1]', true, length: 1);
    }
  
negative.code: mixin M4 implements B {}
  mixin M5 on M2 {}
  ''');
      ClassElement classElementA = findElement.class_('A');
      assertThat(classElementA)
        ..isAncestorOf('B extends A')
        ..isAncestorOf('M1 on A')
  