sprintboot里面当我们使用junit进行测试后的时候，需引入两个依赖：
<dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version><scope>test</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-test</artifactId><version>2.2.6.RELEASE</version><scope>test</scope></dependency>
写测试类也很简单，在类上面添加@SpringBootTest, 然后使用@Autowired引入需要测试service或者mapper， 然后写个测试方法，方法上添加@Test，在方法中调用引入的servcie方法或者mapper方法即可。示例代码：
@SpringBootTestpublic class UserMemberTest {@AutowiredUmsMemberServiceImpl umsMemberServiceImpl;@Testpublic void loginTest(){UserMemberDTO userMemberDTO = new UserMemberDTO();userMemberDTO.setUsername("abc");userMemberDTO.setPassword("123456");String login = umsMemberServiceImpl.login(userMemberDTO);System.out.println(login);}}
我们在执行Test方法的时候，有些人可能会遇到NullPointerException异常：
java.lang.NullPointerExceptionat com.msb.dongbao.ums.UserMemberTest.loginTest(UserMemberTest.java:39)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:498)at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)at org.junit.runners.ParentRunner.run(ParentRunner.java:363)at org.junit.runner.JUnitCore.run(JUnitCore.java:137)at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
明明都@Autowired注入了，为什么会是空对象。之所以会造成这种状况，是因为@Test的类不对，junit有两个Test类，org.junit.Test 和org.junit.jupiter.api.Test
如果引入的类是org.junit.Test，就会出现上面的异常情况。所以我们在引入的时候需要引入org.junit.jupiter.api.Test，org.junit.jupiter.api.Test这个类会模拟sprintboot的启动类，进行注入该注入的对象。所以千万不要引错了类。
