```
  1) Failure:
TestException#test_warning_warn_invalid_argument [/Users/headius/projects/jruby/test/mri/ruby/test_exception.rb:1021]:
[TypeError] exception expected, not.
Class: <Java::JavaLang::ClassCastException>
Message: <"org.jruby.RubyNil cannot be cast to org.jruby.RubyString">
```