谨慎使用 @MockBean注解

我就是我 2022-12-29 02:27 579阅读 0赞

### 目录 ###

*   *   *  问题定位
         *  参考issue
         *  文档释义
         *  解决方案
         *   *  快速方案
         *  相关阅读
         *  其他资料

### 问题定位 ###

@MockBean或@SpyBean会改变bean在context中的状态，为了保证每个test运行时context不被污染而进行刷新，属于正常现象，是springboot的默认行为。但由此会导致其他不可预料的错误。

springboot提供了spirng-boot-starter-test以供开发者使用单元测试，其中org.springframework.boot.test的mockito包，是springboot对org.mockito的增强替换，@MockBean和@SpyBean是主要的mock注解。

tests使用@MockBean和@SpyBean会导致bean在spring test context中缓存的cache key变化，springboot默认缓存context，当顺序执行的两个tests分别依赖不同的但需要被mock的bean或者同一个bean而在其中一个test中需要被mock时（或者其他会污染context的行为），spring test context发生变化，进而引起运行第二个test前刷新context。

于是多个tests重复启动spring test context（较早的context不会自动关闭？jvm中已存在class meta？），不能保证每个tests的执行上下文的独立性、隔离性，某一些bean在被多次创建后会出现异常。

### 参考issue ###

[Spring boot test: context loaded for every test?][Spring boot test_ context loaded for every test]  
[Context not being reused in tests when MockBeans are used][]  
[Context isn’t cached when MockBean using][Context isn_t cached when MockBean using]  
[@SpyBean makes context restart between two tests][SpyBean makes context restart between two tests]

### 文档释义 ###

[Mocking and Spying Beans][]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d0X2JldHRlcg_size_16_color_FFFFFF_t_70]  
[Context Management and Caching][]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d0X2JldHRlcg_size_16_color_FFFFFF_t_70 1]

### 解决方案 ###

#### 快速方案 ####

一、对于非web工程  
将用例中使用的mock变量放到父类，这样所有的用例类都使用同一个上下文，具体的mock放到实际的测试用例类上。

//测试父类
    @RunWith(SpringJUnit4ClassRunner.class)
    public class XxxTestBase { 
        @MockBean
        private BeanService1 beanService1;
    
        @MockBean
        private BeanService2 beanService2;
    
        @MockBean
        private BeanService2 beanService2;
    }
    
    //具体的测试类
    public class ConcreteTest extends XxxTestBase { 
     
        @Test
        public void test() { 
    		beanService2.doTest();
        }
            
    }

二、对于web工程  
如果是web工程，spring context刷新会导致端口冲突，通过设置端口随机来避免。

@springbootTest(class=SOFABootTestApplication.class, WebEnironment=WebEnvironment.RANDOM_PORT)

参考文档：Testing Spring Boot Applications

可能潜在的问题  
1.把该bean不需要被mock的方法一起mock了（@SpyBean替换@MockBean？）；  
2.一些场景下该bean不需要被mock，而上下文中该bean是被mock的；  
3.web工程设置为端口随机，可能会导致某些依赖端口的用例出现失败；

### 相关阅读 ###

[Do You Really Need @DirtiesContext?][Do You Really Need _DirtiesContext]

[Annotation Type DirtiesContext][]

### 其他资料 ###

[Mockito.mock() vs @Mock vs @MockBean][Mockito.mock_ vs _Mock vs _MockBean]  
[Think Twice Before Using @MockBean][Think Twice Before Using _MockBean]

[Spring boot test_ context loaded for every test]: https://stackoverflow.com/questions/48929585/spring-boot-test-context-loaded-for-every-test
[Context not being reused in tests when MockBeans are used]: https://github.com/spring-projects/spring-boot/issues/7174
[Context isn_t cached when MockBean using]: https://github.com/spring-projects/spring-boot/issues/9511
[SpyBean makes context restart between two tests]: https://github.com/spring-projects/spring-boot/issues/12994
[Mocking and Spying Beans]: https://docs.spring.io/spring-boot/docs/current/reference/html/spring-boot-features.html#boot-features-testing
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d0X2JldHRlcg_size_16_color_FFFFFF_t_70]: /images/20221120/acac3abf27ce4ad9a705eec26bc65d23.png
[Context Management and Caching]: https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-testing.html#boot-features-testing-spring-boot-applications-mocking-beans
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d0X2JldHRlcg_size_16_color_FFFFFF_t_70 1]: /images/20221120/dcd8bb9a8b6c404ea465545a81e7c98b.png
[Do You Really Need _DirtiesContext]: http://aikin.me/2018/04/02/do-you-really-need-dirties-context-annotation/
[Annotation Type DirtiesContext]: https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/test/annotation/DirtiesContext.html
[Mockito.mock_ vs _Mock vs _MockBean]: https://editor.csdn.net/md?articleId=111408480
[Think Twice Before Using _MockBean]: http://aikin.me/2018/03/25/think-twice-before-using-mockbean-annotation/