手把手教你实战TDD

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导读

本文将对测试驱动开发（TDD）进行探讨，主要阐述了TDD基本概念理解、TDD常见误区、TDD技术选型等，并提供了贫血模型三层架构和DDD下的TDD实战案例。

领域驱动设计，测试驱动开发。

TDD基本理解

TDD常见的误区

3.1  误区一 单元测试就是TDD

3.2  误区二 误把集成测试当成单元测试

4.1  单元测试框架

4.2  模拟对象框架

4.3  测试覆盖率

4.4  测试报告

5.1  奇怪的计算器

public class StrangeCalculatorTest {    private StrangeCalculator strangeCalculator;    @BeforeEach    public void setup() {      strangeCalculator = new StrangeCalculator();    }    @Test    @DisplayName("入参大于0，将其减1并返回")    public void givenGreaterThan0() {      //大于0的入参      int input = 1;      int expected = 0;      //实际计算      int result = strangeCalculator.calculate(input);      //断言确认是否减1      Assertions.assertEquals(expected, result);    }    @Test    @DisplayName("入参小于0，将其加1并返回")    public void givenLessThan0() {      //小于0的入参      int input = -1;      int expected = 0;      //实际计算      int result = strangeCalculator.calculate(input);      //断言确认是否减1      Assertions.assertEquals(expected, result);    }    @Test    @DisplayName("入参等于0，直接返回")    public void givenEquals0() {      //等于0的入参      int input = 0;      int expected = 0;      //实际计算      int result = strangeCalculator.calculate(input);      //断言确认是否等于0      Assertions.assertEquals(expected, result);    }  }

此时StrangeCalculator类和calculate方法还没有创建，会IDE报红色提醒是正常的。

public class StrangeCalculator {
  public int calculate(int input) {      //此时未实现业务逻辑，因此抛一个不支持操作的异常，以便使测试用例不通过    throw new UnsupportedOperationException();    }  }

• 第二步 绿灯

首先实现givenGreaterThan0这个测试用例对应的逻辑：

public class StrangeCalculator {    public int calculate(int input) {      //大于0的逻辑      if (input > 0) {        return input - 1;      }      //未实现的边界依旧抛出UnsupportedOperationException异常    throw new UnsupportedOperationException();    }  }

注意，目前只实现了input>0的边界条件，其他的条件应该继续抛出异常，以便使其不通过。

继续实现givenLessThan0用例对应的逻辑：

public class StrangeCalculator {    public int calculate(int input) {  
    if (input > 0) {        //大于0的逻辑        return input - 1;      } else if (input < 0) {      //小于0的逻辑        return input + 1;      }      //未实现的边界依旧抛出UnsupportedOperationException异常    throw new UnsupportedOperationException();    }  }

运行单元测试，此时有3个测试用例，其中有1个出错：

图6.此时3个测试用例中只有一个出错

继续实现givenEquals0用例对应的逻辑：

public class StrangeCalculator {    public int calculate(int input) {      //大于0的逻辑      if (input > 0) {        return input - 1;      } else if (input < 0) {        return input + 1;      } else {        return 0;      }    }  }

运行单元测试：此时3个测试用例都通过了：

此时，打开Jacoco的测试覆盖率报告（tdd-example的pom.xml文件中将报告生成的位置配置为target/jacoco-report），打开index.html。

图9、10、11.calculate所有的边界条件都覆盖到了

• 第三步、重构

本案例calculate中只有简单的计算，在实际开发中，进行重构时，可以将具体的业务操作抽取为private方法，例如：

public class StrangeCalculator { 
  public int calculate(int input) {      //大于0的逻辑      if (input > 0) {        return doGivenGreaterThan0(input);      } else if (input < 0) {        return doGivenLessThan0(input);      } else {        return doGivenEquals0(input);      }    }    private int doGivenEquals0(int input) {      return 0;    }    private int doGivenLessThan0(int input) {      return input + 1;    }    private int doGivenGreaterThan0(int input) {      return input - 1;    }  }

再次执行单元测试，测试通过。

图13.Jacoco覆盖率的报告显示每个边界条件都被覆盖到

5.1.2 第二次迭代

奇怪的计算器第二次迭代的需求如下：

第二个版本的需求对上一个迭代的边界条件做了调整，需要先根据本次迭代，整理出新的、完整的边界条件：

（1）针对大于0且小于100的input，计算其平方值；

（2）针对大于等于100的input，计算其减去1的值；

（3）针对小于0的input,计算其加1的值；

• 第一步，红灯

@Test  @DisplayName("入参大于0且小于100，计算其平方")  public void givenGreaterThan0AndLessThan100() {  
  int input = 3;    int expected = 9;    //实际计算    int result = strangeCalculator.calculate(input);    //断言确认是否计算了平方    Assertions.assertEquals(expected, result);  }  @Test  @DisplayName("入参大于等于100，计算其减1的值")  public void givenGreaterThanOrEquals100() {    int input = 100;    int expected = 99;    //实际计算    int result = strangeCalculator.calculate(input);    //断言确认是否计算了平方    Assertions.assertEquals(expected, result);  }

运行所有单元测试，可以看到有测试用例没有通过：

• 第二步、绿灯

实现第二次迭代的业务逻辑：

public class StrangeCalculator {
  public int calculate(int input) {      if (input >= 100) {        //第二次迭代时，大于等于100的区间还是走老逻辑        return doGivenGreaterThan0(input);      } else if (input > 0) {        //第二次迭代的业务逻辑        return input * input;      } else if (input < 0) {        return doGivenLessThan0(input);      } else {        return doGivenEquals0(input);      }    }    private int doGivenEquals0(int input) {      return 0;    }    private int doGivenLessThan0(int input) {      return input + 1;    }    private int doGivenGreaterThan0(int input) {      return input - 1;    }  }

执行所有的测试用例，此时第二次迭代的givenGreaterThan0AndLessThan100和givenGreaterThanOrEquals100这两个用例都通过了，但是givenGreaterThan0却没有通过：

审查之前迭代的单元测试用例，可以看到givenGreaterThan0的边界已经被givenGreaterThan0AndLessThan100和givenGreaterThanOrEquals100覆盖到了。

一方面givenGreaterThan0对应的业务逻辑改变了，一方面已经有其他测试用例覆盖了givenGreaterThan0的边界条件，因此，可以将givenGreaterThan0移除了。

@Test  @DisplayName("入参大于0，将其减1并返回")  public void givenGreaterThan0() {    int input = 1;    int expected = 0;    int result = strangeCalculator.calculate(input);    Assertions.assertEquals(expected, result);  }
@Test  @DisplayName("入参大于0且小于100，计算其平方")  public void givenGreaterThan0AndLessThan100() {    //于0且小于100的入参    int input = 3;    int expected = 9;    //实际计算    int result = strangeCalculator.calculate(input);    //断言确认是否计算了平方    Assertions.assertEquals(expected, result);  }  @Test  @DisplayName("入参大于等于100，计算其减1的值")  public void givenGreaterThanOrEquals100() {    //于0且小于100的入参    int input = 100;    int expected = 99;    //实际计算    int result = strangeCalculator.calculate(input);    //断言确认是否计算了平方    Assertions.assertEquals(expected, result);  }

将givenGreaterThan0移除后，重新执行单元测试：

• 第三步、重构

public class StrangeCalculator {  
  public int calculate(int input) {      if (input >= 100) {        //第二次迭代时，大于等于100的区间还是走老逻辑        // return doGivenGreaterThan0(input);        return doGivenGreaterThanOrEquals100(input);      } else if (input > 0) {      //第二次迭代的业务逻辑      return doGivenGreaterThan0AndLessThan100(input);      } else if (input < 0) {        return doGivenLessThan0(input);      } else {        return doGivenEquals0(input);      }    }    private int doGivenGreaterThan0AndLessThan100(int input) {      return input * input;    }    private int doGivenEquals0(int input) {      return 0;    }    private int doGivenGreaterThanOrEquals100(int input) {      return input + 1;    }    private int doGivenGreaterThan100(int input) {      return input - 1;    }  }

5.1.3 第三次迭代

5.2  贫血模型三层架构的TDD实战

public interface CmsArticleMapper {    int deleteByPrimaryKey(Long id);  
  int insert(CmsArticle record);  
  CmsArticle selectByPrimaryKey(Long id);  
  List<CmsArticle> selectAll();  
  int updateByPrimaryKey(CmsArticle record);  }

@ExtendWith(SpringExtension.class)  @SpringBootTest  @AutoConfigureTestDatabase  public class CmsArticleMapperTest {    @Resource    private CmsArticleMapper mapper;    @Test    public void testInsert() {      CmsArticle article = new CmsArticle();      article.setId(0L);      article.setArticleId("ABC123");      article.setContent("content");      article.setTitle("title");      article.setVersion(1L);      article.setModifiedTime(new Date());      article.setDeleted(0);      article.setPublishState(0);      int inserted = mapper.insert(article);      Assertions.assertEquals(1, inserted);    }    @Test    public void testUpdateByPrimaryKey() {      CmsArticle article = new CmsArticle();      article.setId(1L);      article.setArticleId("ABC123");      article.setContent("content");      article.setTitle("title");      article.setVersion(1L);      article.setModifiedTime(new Date());      article.setDeleted(0);      article.setPublishState(0);      int updated = mapper.updateByPrimaryKey(article);      Assertions.assertEquals(1, updated);    }    @Test    public void testSelectByPrimaryKey() {      CmsArticle article = mapper.selectByPrimaryKey(2L);      Assertions.assertNotNull(article);      Assertions.assertNotNull(article.getTitle());      Assertions.assertNotNull(article.getContent());    }  }

@Service  public class ArticleServiceImpl implements ArticleService {    @Resource    private CmsArticleMapper mapper;    @Resource    private IdServiceGateway idServiceGateway;    @Override    public void createDraft(CreateDraftCmd cmd) {      CmsArticle article = new CmsArticle();      article.setArticleId(idServiceGateway.nextId());      article.setContent(cmd.getContent());      article.setTitle(cmd.getTitle());      article.setPublishState(0);      article.setVersion(1L);      article.setCreatedTime(new Date());      article.setModifiedTime(new Date());      article.setDeleted(0);      mapper.insert(article);    }    @Override    public CmsArticle getById(Long id) {      return mapper.selectByPrimaryKey(id);    }  }

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE,  classes = {ArticleServiceImpl.class})  @ExtendWith(SpringExtension.class)  public class ArticleServiceImplTest {    @Resource    private ArticleService articleService;    @MockBean    IdServiceGateway idServiceGateway;    @MockBean    private CmsArticleMapper cmsArticleMapper;    @Test    public void testCreateDraft() {      Mockito.when(idServiceGateway.nextId()).thenReturn("123");      Mockito.when(cmsArticleMapper.insert(Mockito.any())).thenReturn(1);      CreateDraftCmd createDraftCmd = new CreateDraftCmd();      createDraftCmd.setTitle("test-title");      createDraftCmd.setContent("test-content");      articleService.createDraft(createDraftCmd);      Mockito.verify(idServiceGateway, Mockito.times(1)).nextId();      Mockito.verify(cmsArticleMapper, Mockito.times(1)).insert(Mockito.any());    }    @Test    public void testGetById() {      CmsArticle article = new CmsArticle();      article.setId(1L);      article.setTitle("testGetById");      Mockito.when(cmsArticleMapper.selectByPrimaryKey(Mockito.any())).thenReturn(article);      CmsArticle byId = articleService.getById(1L);      Assertions.assertNotNull(byId);      Assertions.assertEquals(1L,byId.getId());      Assertions.assertEquals("testGetById",byId.getTitle());    }}

@RestController  @RequestMapping("/article")  public class ArticleController {    @Resource    private ArticleService articleService;    @RequestMapping("/createDraft")    public void createDraft(@RequestBody CreateDraftCmd cmd) {      articleService.createDraft(cmd);    }    @RequestMapping("/get")    public CmsArticle get(Long id) {      CmsArticle article = articleService.getById(id);      return article;    }}

@ExtendWith(SpringExtension.class)  @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.MOCK,  classes = {ArticleController.class})  @EnableWebMvc  public class ArticleControllerTest {    @Resource    WebApplicationContext webApplicationContext;    MockMvc mockMvc;    @MockBean    ArticleService articleService;    //初始化mockmvc    @BeforeEach    void setUp() {      mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext).build();    }    @Test    void testCreateDraft() throws Exception {      CreateDraftCmd cmd = new CreateDraftCmd();      cmd.setTitle("test-controller-title");      cmd.setContent("test-controller-content");      ObjectMapper mapper = new ObjectMapper();      String valueAsString = mapper.writeValueAsString(cmd);      Mockito.doNothing().when(articleService).createDraft(Mockito.any());      mockMvc.perform(MockMvcRequestBuilders      //访问的URL和参数      .post("/article/createDraft")      .content(valueAsString)      .contentType(MediaType.APPLICATION_JSON))      //期望返回的状态码      .andExpect(MockMvcResultMatchers.status().isOk())      //输出请求和响应结果      .andDo(MockMvcResultHandlers.print()).andReturn();    }    @Test    void testGet() throws Exception {      CmsArticle article = new CmsArticle();      article.setId(1L);      article.setTitle("testGetById");      Mockito.when(articleService.getById(Mockito.any())).thenReturn(article);      mockMvc.perform(MockMvcRequestBuilders      //访问的URL和参数      .get("/article/get").param("id","1"))      //期望返回的状态码      .andExpect(MockMvcResultMatchers.status().isOk())    .andExpect(MockMvcResultMatchers.jsonPath("$.id").value(1L))    //输出请求和响应结果      .andDo(MockMvcResultHandlers.print()).andReturn();    }  }

5.3  DDD下的TDD实战

@Data  public class ArticleEntity extends AbstractDomainMask {    /**    * article业务主键    */    private ArticleId articleId;    /**    * 标题    */    private ArticleTitle title;    /**    * 内容    */    private ArticleContent content;    /**    * 发布状态，[0-待发布；1-已发布]    */    private Integer publishState;    /**    * 创建草稿    */    public void createDraft() {      this.publishState = PublishState.TO_PUBLISH.getCode();    }    /**    * 修改标题    *    * @param articleTitle    */    public void modifyTitle(ArticleTitle articleTitle) {      this.title = articleTitle;    }    /**    * 修改正文    *    * @param articleContent    */    public void modifyContent(ArticleContent articleContent) {      this.content = articleContent;    }    /**    * 发布    */  public void publishArticle() {      this.publishState = PublishState.PUBLISHED.getCode();    }  }

public class ArticleEntityTest {    @Test    @DisplayName("创建草稿")    public void testCreateDraft() {      ArticleEntity entity = new ArticleEntity();      entity.setTitle(new ArticleTitle("title"));      entity.setContent(new ArticleContent("content12345677890"));      entity.createDraft();      Assertions.assertEquals(PublishState.TO_PUBLISH.getCode(), entity.getPublishState());    }    @Test    @DisplayName("修改标题")    public void testModifyTitle() {      ArticleEntity entity = new ArticleEntity();      entity.setTitle(new ArticleTitle("title"));      entity.setContent(new ArticleContent("content12345677890"));      ArticleTitle articleTitle = new ArticleTitle("new-title");      entity.modifyTitle(articleTitle);      Assertions.assertEquals(articleTitle.getValue(), entity.getTitle().getValue());    }    @Test    @DisplayName("修改正文")    public void testModifyContent() {      ArticleEntity entity = new ArticleEntity();      entity.setTitle(new ArticleTitle("title"));      entity.setContent(new ArticleContent("content12345677890"));      ArticleContent articleContent = new ArticleContent("new-content12345677890");      entity.modifyContent(articleContent);      Assertions.assertEquals(articleContent.getValue(), entity.getContent().getValue());    }    @Test    @DisplayName("发布")    public void testPublishArticle() {      ArticleEntity entity = new ArticleEntity();      entity.setTitle(new ArticleTitle("title"));      entity.setContent(new ArticleContent("content12345677890"));      entity.publishArticle();      Assertions.assertEquals(PublishState.PUBLISHED.getCode(), entity.getPublishState());    }  }

public class ArticleTitle implements ValueObject<String> {    private final String value;    public ArticleTitle(String value) {      this.check(value);      this.value = value;    }    private void check(String value) {      Objects.requireNonNull(value, "标题不能为空");      if (value.length() > 64) {        throw new IllegalArgumentException("标题过长");      }    }    @Override    public String getValue() {      return this.value;    }  }

public class ArticleTitleTest {    @Test    @DisplayName("测试业务规则，ArticleTitle为空抛异常")    public void whenGivenNull() {      Assertions.assertThrows(NullPointerException.class, () -> {        new ArticleTitle(null);      });    }    @Test    @DisplayName("测试业务规则，ArticleTitle值长度大于64抛异常")    public void whenGivenLengthGreaterThan64() {      Assertions.assertThrows(IllegalArgumentException.class, () -> {        new ArticleTitle("11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111");      });    }    @Test    @DisplayName("测试业务规则，ArticleTitle小于等于64正常创建")    public void whenGivenLengthEquals64() {      ArticleTitle articleTitle = new ArticleTitle("1111111111111111111111111111111111111111111111111111111111111111");     Assertions.assertEquals(64, articleTitle.getValue().length());    }  }

@Component  public class ArticleDomainFactoryImpl implements ArticleFactory {  @Override    public ArticleEntity newInstance(ArticleTitle title, ArticleContent content) {      ArticleEntity entity = new ArticleEntity();      entity.setTitle(title);      entity.setContent(content);      entity.setArticleId(new ArticleId(UUID.randomUUID().toString()));      entity.setPublishState(PublishState.TO_PUBLISH.getCode());      entity.setDeleted(0);      Date date = new Date();      entity.setCreatedTime(date);      entity.setModifiedTime(date);      return entity;    }  }

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE,  classes = {ArticleDomainFactoryImpl.class})  @ExtendWith(SpringExtension.class)  public class ArticleDomainFactoryImplTest {    @Resource    private ArticleFactory articleFactory;    @Test    @DisplayName("Factory创建新实体")    public void testNewInstance() {      ArticleTitle articleTitle = new ArticleTitle("title");      ArticleContent articleContent = new ArticleContent("content1234567890");      ArticleEntity instance = articleFactory.newInstance(articleTitle, articleContent);      // 创建新实体    Assertions.assertNotNull(instance);     // 唯一标识正确赋值    Assertions.assertNotNull(instance.getArticleId());   }  }

总结

本文介绍了TDD的基本概念和实施方法，并提供了贫血模型三层架构和DDD下的TDD实战案例。要理解做出任何改变都会有一个艰难的开始，将现有的软件开发方法转变为TDD也不例外，但只要坚持下去，最终必定能从TDD中受益。

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