MockExecutor mock = new MockExecutor();
    TestExecutor testExecutor = new TestExecutor(mock);

    Future<?> unused1 = testExecutor.schedule(DO_NOTHING, 10, MINUTES);
    mock.assertLastMethodCalled("scheduleRunnable", 10, MINUTES);

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

  public void testSchedule_repeating() {