I need to focus attention elsewhere for a while, so can't work on converting this test right now and will unassign myself.
I attached a patch with how far I got so far just in case somebody else is interested in picking it up. You're welcome to use it as a starting point (or toss it and start over). If nobody has picked it up by the time I can focus time on it again, I'll pick it back up.
The patch sets up the JUnit framework and converts just the first two tests in lang/procedure.java: testNegative and testDelayedClassChecking, and it splits testNegative, which I thought was kind of long, into two methods:
testCreateRoutineErrors still uses the old statementExceptionExpected() method from procedure.java, but with arguments swapped around to match assertStatementError. It should be able to use the BaseJDBCTestCase assertStatementError method (testMethodSignatureDerby258 uses it just fine, as does the XMLTypeAndOpsTest suite). The cause is probably staring me right in the face and I'm not seeing it.