Debugging rails application is very easy. Install ruby-debugger gem gem install ruby-debugger Then you simply have to start server with: ruby script/server --debugger debugger only works with Mongrel and Webrick In your code you can put debugger every where you need it When the line after debugger command has to be executed the server stops and allows you to debug your code. Typing help command you will see the list of commands available: list shows the code under execution next goes to the next line to be executed continue continue to execution of the code p variable_name print the current value of the variable_name irb lunch the console through wich you can modify variables value |