[Webtest] Need the traceback for an unexpected exception

[Janet Hurwitz]

The results file shows only 

com.canoo.webtest.engine.StepExecutionException
Unexpected exception caught: java.lang.StackOverflowError

How can I get the traceback?

Also, at one point I had my webtest log directed to a file. I can't for the life
of me remember how I did that or find the information in the docs. What do I
need to change?
(The webtest log in the console didn't show the traceback info, so it won't help
in the above case, but would like to know for the future.)

Thanks,
Janet