@Test
public void testCancelOperation() throws Exception {

  String opName = "testCancelOperation";
  LongRunningClient longRunningClient = mockCancelOperation(StatusCode.Code.OK);
  ClientContext mockContext = getClientContext(new FakeChannel(), executor);
  OperationCallable<Integer, Color, Currency> callable =
      FakeCallableFactory.createOperationCallable(
          getUnexpectedStartCallable(), callSettings, mockContext, longRunningClient);
  ApiFuture<Void> future = callable.cancel(opName);
  assertThat(future.get()).isNull();
}