@Test
public void testOperationCancelled() {

  tracedCallable.call("test", responseObserver, callContext);
  responseObserver.getController().cancel();
  MockServerStreamingCall<String, String> innerCall = innerCallable.popLastCall();
  innerCall
      .getController()
      .getObserver()
      .onError(
          new CancelledException("fake cancel", null, new FakeStatusCode(Code.CANCELLED), false));
  assertThat(responseObserver.isDone()).isTrue();
  verify(tracer, times(1)).operationCancelled();
}