Junit target not working from Ant script

The most common cause is that the file junit.jar is not present int the $ANT_HOME/lib folder. The ant task "junit .." uses ant-junit.jar which in turn depends on the junit.jar. Make sure that junit.jar is in classpath.

Attaching a debugger to Java tasks launched by Ant

Set this env variable and then launch your ant command. 

ANT_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,address=8044,server=y,suspend=n"