rubinius/rubinius — pull request #1829 by LTe (2012-07-25 08:02:44+00:00)
Title: Array#join executed with nil should use default separator

Add specs for join with nil argument.

https://github.com/ruby/ruby/commit/61a67bc7200a5bf38ce77acc8fb11fa682bedbd8
http://bugs.ruby-lang.org/issues/5915