* to any {@code Runnable} passed to the default implementation of {@link #wrapTask(Runnable)}.
   */
  protected abstract <T extends @Nullable Object> Callable<T> wrapTask(Callable<T> callable);

  /**
   * Wraps a {@code Runnable} for submission to the underlying executor. The default implementation
   * delegates to {@link #wrapTask(Callable)}.
   */
  protected Runnable wrapTask(Runnable command) {

    TestExecutor(MockExecutor mock) {
      super(mock);
    }

    @Override
    protected <T> Callable<T> wrapTask(Callable<T> callable) {
      return new WrappedCallable<T>(callable);
    }

    @Override
    protected Runnable wrapTask(Runnable command) {
      return new WrappedRunnable(command);
    }
  }

    TestExecutor(MockExecutor mock) {
      super(mock);
    }

    @Override
    protected <T> Callable<T> wrapTask(Callable<T> callable) {
      return new WrappedCallable<T>(callable);
    }

    @Override
    protected Runnable wrapTask(Runnable command) {
      return new WrappedRunnable(command);
    }
  }