when i use debugger in the spec , after type irb , it raise error below
INTERNAL ERROR!!! wrong number of arguments (2 for 1) /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/extend-command.rb:157:in `respond_to?' /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/extend-command.rb:157:in `install_alias_method' /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/extend-command.rb:179:in `extend_object' /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/extend-command.rb:178:in `each' /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/extend-command.rb:178:in `extend_object' /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:93:in `extend' /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:93:in `initialize' /Library/Ruby/Gems/1.8/gems/ruby-debug-0.10.1/cli/ruby-debug/commands/irb.rb:24:in `new' /Library/Ruby/Gems/1.8/gems/ruby-debug-0.10.1/cli/ruby-debug/commands/irb.rb:24:in `start_session' /Library/Ruby/Gems/1.8/gems/ruby-debug-0.10.1/cli/ruby-debug/commands/irb.rb:62:in `execute' /Library/Ruby/Gems/1.8/gems/ruby-debug-0.10.1/cli/ruby-debug/processor.rb:272:in `one_cmd' /Library/Ruby/Gems/1.8/gems/ruby-debug-0.10.1/cli/ruby-debug/processor.rb:259:in `process_commands' /Library/Ruby/Gems/1.8/gems/ruby-debug-0.10.1/cli/ruby-debug/processor.rb:258:in `each' /Library/Ruby/Gems/1.8/gems/ruby-debug-0.10.1/cli/ruby-debug/processor.rb:258:in `process_commands' /Library/Ruby/Gems/1.8/gems/ruby-debug-0.10.1/cli/ruby-debug/processor.rb:251:in `catch' /Library/Ruby/Gems/1.8/gems/ruby-debug-0.10.1/cli/ruby-debug/processor.rb:251:in `process_commands' /Library/Ruby/Gems/1.8/gems/ruby-debug-0.10.1/cli/ruby-debug/processor.rb:171:in `__at_line' (eval):5:in `at_line' (eval):3:in `synchronize' (eval):3:in `at_line' /Library/Ruby/Gems/1.8/gems/ruby-debug-base-0.10.1/lib/ruby-debug-base.rb:52:in `at_line' ./spec/models/diagnosis_spec.rb:16 /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/example/example_methods.rb:84:in `instance_eval' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/example/example_methods.rb:84:in `run_with_description_capturing' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/example/example_methods.rb:21:in `execute' /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/timeout.rb:48:in `timeout' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/example/example_methods.rb:18:in `execute' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/example/example_group_methods.rb:303:in `execute_examples' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/example/example_group_methods.rb:302:in `each' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/example/example_group_methods.rb:302:in `execute_examples' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/example/example_group_methods.rb:130:in `run' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/runner/example_group_runner.rb:22:in `run' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/runner/example_group_runner.rb:21:in `each' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/runner/example_group_runner.rb:21:in `run' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/runner/options.rb:106:in `run_examples' /Users/sunsware/sandbox/dxj/vendor/plugins/rspec/lib/spec/runner/command_line.rb:19:in `run' ./script/spec:4...