MockExecutor mock = new MockExecutor();
    TestExecutor testExecutor = new TestExecutor(mock);
    testExecutor.execute(doNothing());
    mock.assertLastMethodCalled("execute");
  }

  public void testSubmit() throws InterruptedException, ExecutionException {
    {
      MockExecutor mock = new MockExecutor();
      TestExecutor testExecutor = new TestExecutor(mock);
      Future<?> f = testExecutor.submit(doNothing());