在maven project中，test case的运行是少不了的。随着项目复杂度的增加，相应的test cases的数量也会随之增加。
突然有一天，用eclipse 内置的m2e插件Run as -> Maven test运行test cases，跑着跑着就报错如下：
“java.lang.OutOfMemoryError: PermGen space” error
Google了各种办法之后没有解决：
1.add 环境变量：
Windows: set MAVEN_OPTS=-Xmx512m -XX:MaxPermSize=1024m
Linux: export MAVEN_OPTS="-Xmx512m -XX:MaxPermSize=1024m"
2. adding -XX:MaxPermSize=1024M and -XX:PermSize=512M after -vmargs in the eclipse.ini
3. adding -XX:MaxPermSize=1024m and -XX:PermSize=512m to my Tomcat launch configuration
4. add VM arguments on my default JRE as following:Window -> Preferences -> Java -> Installed JREs. Select the checked JRE/JDK and click edit, and set Default VM Arguments = -Xms128m - Xmx1024m -XX:MaxPermSize=1024m
以上四种办法试了个遍，不知道是我打开的方式不对还是怎么回事儿，没有一个起作用，最后按照一篇博文(https://eureka.ykyuen.info/2010/03/02/maven-set-java-heap-memory-for-junit-in-maven-surefire-plugin/)中的设置，在pom.xml中添加参数如下：
<
plugin
>
<
groupId
>org.apache.maven.plugins
groupId
>
<
artifactId
>maven-surefire-plugin
artifactId
>
<
version
>2.18.1
version
>
<
configuration
>
<
argLine
>-XX:MaxPermSize=1024m
argLine
>
configuration
>
plugin
>
设置完了之后，再次运行mvn test or Run as ->Maven test，顺利跑完整个test。
博文中写到：
JUnit tests ignore the environment variable MAVEN_OPTS and the JVM settings in Run Configurations.
So if u have OutOfMemoryError when running unit test in Maven, you have to set the Java Heap Memory in the maven-surefire-plugin inside the pom.xml.
在Stackoverflow(http://stackoverflow.com/questions/2819853/setting-java-heap-space-under-maven-2-on-windows) 有个post写到：
Basically the JUnits fork off into their own environment and ignore the settings in MAVEN_OPTS. You need to configure surefire in your pom to add more memory for the JUnits.
参考链接：
http://stackoverflow.com/questions/3101128/java-lang-outofmemoryerror-permgen-space-in-maven-build
http://stackoverflow.com/questions/24708077/java-lang-outofmemoryerror-permgen-space-after-convering-project-to-maven
http://stackoverflow.com/questions/2819853/setting-java-heap-space-under-maven-2-on-windows
https://eureka.ykyuen.info/2010/03/02/maven-set-java-heap-memory-for-junit-in-maven-surefire-plugin/