Mocha is required by setup_and_teardown.rb in all environments and modes

The following code snippet is where it happens. Mocha becomes available in all environments, and also in script/console, script/server, etc.

        begin
          require 'mocha'
          base.alias_method_chain :run, :callbacks_and_mocha
        rescue LoadError
          base.alias_method_chain :run, :callbacks
        end

This could cause other testing frameworks or even test/unit tests to encounter problems as mocha will be included along side whatever mocking framework the user actually is using. This doesn't seem to cause any issues currently, but it definitely should be cleaned up.