JUnit.org Resources for Test Driven Development

How do I define junit target in ant so it knows where to find Oracle database?
Or does it somehow know where to find database based on other settings in project,
like web or spring config files?
I've got a bunch of junit tests that run fine if I launch them from within eclipse.
But if I try to run them directly via ant build script, they all die with the strange error:
Error 'Unexpected failure during bean definition parsing in resource URL [file:spring-misc-junit.xml] at:
Bean 'mailSender'; nested exception is java.lang.SecurityException: class
“javax.mail.AuthenticationFailedException”’s signer information does not match signer information of other classes in the same package.

Thought maybe ant wasn't able to figure out how to authenticate to database or ldap, but I'm just
grasping at anything....

I guess I don't understand the flow of how ant works, what it knows about or what it needs to be
told about to run the tests.....