public ProtoFluentAssertion comparingExpectedFieldsOnly() {
    return usingConfig(config.comparingExpectedFieldsOnly());
  }
@Test
  public void testComparingExpectedFieldsOnly() {
    Message message = parse("o_int: 3 r_string: 'foo'");
    Message narrowMessage = parse("o_int: 3");

    expectThat(message).comparingExpectedFieldsOnly().isEqualTo(narrowMessage);
    expectThat(narrowMessage).comparingExpectedFieldsOnly().isNotEqualTo(message);

    expectFailureWhenTesting()
        .that(message)
        .comparingExpectedFieldsOnly()
        .isNotEqualTo(narrowMessage);
    expectThatFailure().hasMessageThat().contains("ignored: r_string");
  }