Like most people I prefer to use centos supplied apps from their repos as it just makes keeping things updated easier. So I use the eclipse supplied by centos which does not have Junit4 if you would like to enable it here are the steps I followed:
1.Download eclipse from there site the .tar version
2.Extract folder org.junit4_4.5.0.v20090423 and file org.eclipse.jdt.junit4.runtime_1.1.0.v20090513-2000.jar and copy them to folder /usr/share/eclipse/plugins/ download file junit-4.1jar and place it in folder org.junit4_4.5.0.v20090423
3.Restart eclipse and you should be set. Happy Testing!!!!
NB: Depending on the eclipse version you download the numbers on the folders and files may be different, and incase the new versions require a different file than junit-4.1.jar eclispe will tell you the new version needed.
the Junit-4.1.jar I used is here or you can google it if you want.