public String getThumbnailContent() {
        return Arrays.stream(content.split(LINE_BREAK))
                .limit(THUMBNAIL_LINE_HEIGHT)
                .collect(Collectors.joining(LINE_BREAK));
    }
@Test
    @DisplayName("성공: 썸네일(5줄) 추출 잘 되는지 확인")
    void getThumbnailContent() {
        // given
        Member member = MemberFixture.getFirstMember();
        Category category = CategoryFixture.getFirstCategory();
        Template template = new Template(member, "title", "description", category);
        SourceCode sourceCode = new SourceCode(
                1L,
                template,
                "file",
                "1\n2\n3\n4\n5\n6\n7\n8\n9\n",
                1
        );

        // when
        String thumbnail = sourceCode.getThumbnailContent();

        // then
        assertThat(thumbnail).isEqualTo("1\n2\n3\n4\n5");
    }