@Test
  public void should_return_true_when_input_correct() throws IOException {
    guessCenter.generateNum();

    Num result = guessCenter.guess("1234");
    assertThat(result.isCorrect(), is(true));
  }
  @Test
  public void should_return_false_when_input_incorrect() throws IOException {
    guessCenter.generateNum();

    Num result = guessCenter.guess("5678");
    assertThat(result.isCorrect(), is(false));
  }