java.lang.NoClassDefFoundError: org/hamcrest/SelfDescribing

Java 使用 junit 的时候报异常，提示找不到类：

java.lang.NoClassDefFoundError: org/hamcrest/SelfDescribing
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
	at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
	at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
	at java.lang.Class.getDeclaredConstructors0(Native Method)
	at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389)
	at java.lang.Class.getConstructor0(Class.java:2699)
	at java.lang.Class.getConstructor(Class.java:1657)
	at org.junit.internal.builders.AnnotatedBuilder.buildRunner(AnnotatedBuilder.java:29)
	at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:21)
	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.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.(JUnit4TestReference.java:33)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestClassReference.(JUnit4TestClassReference.java:25)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestLoader.createTest(JUnit4TestLoader.java:48)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestLoader.loadTests(JUnit4TestLoader.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:452)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: java.lang.ClassNotFoundException: org.hamcrest.SelfDescribing
	at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
	at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)

分析原因：

1、首先检查是否缺少hamcrest包，如果不存在添加hamcrest包（hamcrest-core-1.3.jar）

2、右键点击项目-属性-Java Build Path-Source-Output Folder-设置成：项目名称/target/test-classes