今天在写代码的时候，老是报错：java.lang.NoClassDefFoundError:
org/hamcrest/SelfDescribing。
后来查发现有人说换一个低版本的就行了，引入junit4.10.jar。果然行了，但是我们要知其然，更要只其所以然
查官网：JUnit now uses the latest version ofHamcrest. Thus, you can use all the available matchers and benefit from animprovedassertThatwhich will now print the mismatchdescription 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.
junit-dep.jar: Only includes the JUnit classes but not Hamcrest. Lets you use a different Hamcrest version.
注意黑色加下划线的部分意思是4.11以上版本不在包含hamcrest。
所以现在有两个办法解决：
1.junit版本降到4.10
2.导入hamcrest-core-1.3.jar
https://central.sonatype.com/artifact/junit/junit/4.10/versions
