Future<?> unused2 = testExecutor.schedule(callable(DO_NOTHING), 5, SECONDS);
    mock.assertLastMethodCalled("scheduleCallable", 5, SECONDS);
  }

  public void testSchedule_repeating() {
    MockExecutor mock = new MockExecutor();
    TestExecutor testExecutor = new TestExecutor(mock);
    @SuppressWarnings("unused") // https://errorprone.info/bugpattern/FutureReturnValueIgnored