junit测试遇到的问题：java.lang.NoClassDefFoundError: org/hamcrest/SelfDescribing

问题

今天在测试代码的时候报如下错误：

java.lang.NoClassDefFoundError: org/hamcrest/SelfDescribing

	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at org.junit.internal.builders.JUnit4Builder.runnerForClass(JUnit4Builder.java:10)
	at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
	at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:26)
	at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
	at org.junit.internal.requests.ClassRequest.getRunner(ClassRequest.java:26)
	at org.junit.internal.requests.FilterRequest.getRunner(FilterRequest.java:31)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:49)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
Caused by: java.lang.ClassNotFoundException: org.hamcrest.SelfDescribing
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	... 22 more

排查原因

根据 提示应该是缺少类SelfDescribing导致的，经过翻阅文档，发现在junit4.11之后的版本就不再包含hamcrest包，需要添加hamcrest-core.jar包。

参考官网资料：

JUnit now uses the latest version of Hamcrest. Thus, you can use all the available matchers and benefit from an improved assertThat which will now print the mismatch description from the matcher when an assertion fails.


junit.jar: Includes the Hamcrest classes. The simple all-in-one solution to get started quickly.`Starting with version 4.11`, Hamcrest is` no longer` included in this jar.

解决

两种解决方法：

1、不改变Junit的版本，添加hamcrest-core包：

 <dependency>
          <groupId>junitgroupId>
          <artifactId>junitartifactId>
          <version>4.12version>
          <scope>testscope>
      dependency>

<dependency>
    <groupId>org.hamcrestgroupId>
    <artifactId>hamcrest-coreartifactId>
    <version>2.2version>
    <scope>testscope>
dependency>

2、换成低版本的Junit

 <dependency>
          <groupId>junitgroupId>
          <artifactId>junitartifactId>
          <version>4.10version>
          <scope>testscope>
 dependency>