Testing problems: ActiveSupport

Hey everybody,

I am trying to test a small application with a simple testing, but I get the following errors while using Aptana 2.0.5 with Ruby 1.9.1 and Rails 2.3.8(I know why I get the first one, but I'm not sure about the ActiveSupport errors):

Exception: undefined method `screen_name' for nil:NilClass C:/Ruby191/lib/ruby/gems/1.9.1/gems/activesupport-2.3.8/lib/active_support/whiny_nil.rb:52:in `method_missing' D:/Projects/RailsSpace/test/functional/user_controller_test.rb:39:in `try_to_login' D:/Projects/RailsSpace/test/functional/user_controller_test.rb:28:in `testing_logout' C:/Ruby191/lib/ruby/gems/1.9.1/gems/activesupport-2.3.8/lib/active_support/testing/setup_and_teardown.rb:62:in `run' C:/Ruby191/lib/ruby/gems/1.9.1/gems/test-unit-2.1.0/lib/test/unit/testsuite.rb:38:in `block in run' C:/Ruby191/lib/ruby/gems/1.9.1/gems/test-unit-2.1.0/lib/test/unit/testsuite.rb:37:in `each' C:/Ruby191/lib/ruby/gems/1.9.1/gems/test-unit-2.1.0/lib/test/unit/testsuite.rb:37:in `run' C:/Ruby191/lib/ruby/gems/1.9.1/gems/test-unit-2.1.0/lib/test/unit/testsuite.rb:38:in `block in run' C:/Ruby191/lib/ruby/gems/1.9.1/gems/test-unit-2.1.0/lib/test/unit/testsuite.rb:37:in `each' C:/Ruby191/lib/ruby/gems/1.9.1/gems/test-unit-2.1.0/lib/test/unit/testsuite.rb:37:in `run' C:/Ruby191/lib/ruby/gems/1.9.1/gems/test-unit-2.1.0/lib/test/unit/ui/testrunnermediator.rb:48:in `run_suite' D:/Projects/.metadata/.plugins/org.rubypeople.rdt.testunit/ruby/RemoteTestRunner.rb:117:in `start_mediator' D:/Projects/.metadata/.plugins/org.rubypeople.rdt.testunit/ruby/RemoteTestRunner.rb:62:in `start' D:/Projects/.metadata/.plugins/org.rubypeople.rdt.testunit/ruby/RemoteTestRunner.rb:332:in `<main>'

Thanks a lot to everybody in advance!