JUnits are not running in eclipse

When I am trying to execute the JUnit files in my ee i m getting a message like

Launching .java config does not exists.

And some times I am getting an exception like "ClassNotFoundExceptions".

If any one of you encountered this issue, Please let me know is there any alternatives in order to execute the JUnits from Ee.

Note:

By using the Ant commands we are executing, but my custom test cases are not there in the generated report.