public CheckboxAnswer getAnswerByQuestionId(long questionId) {
        if (!checkboxAnswers.containsKey(questionId)) {
            throw new MissingCheckboxAnswerForQuestionException(questionId);
        }
        return checkboxAnswers.get(questionId);
    }
@Test
    void 질문_ID로_선택형_답변을_반환한다() {
        // given
        CheckboxAnswers checkboxAnswers = new CheckboxAnswers(List.of(new CheckboxAnswer(1, List.of(1L))));

        // when
        CheckboxAnswer actual = checkboxAnswers.getAnswerByQuestionId(1);

        // then
        assertThat(actual.getSelectedOptionIds())
                .extracting(CheckBoxAnswerSelectedOption::getSelectedOptionId)
                .containsExactly(1L);
    }