If you ever get this error:
can't link outside actor context
Followed by something like:
/Library/Ruby/Gems/2.0.0/gems/celluloid-0.16.0/lib/celluloid.rb:176:in `new_link' /Library/Ruby/Gems/2.0.0/gems/sidekiq-3.3.4/lib/sidekiq/launcher.rb:21:in `initialize' /Library/Ruby/Gems/2.0.0/gems/sidekiq-3.3.4/lib/sidekiq/cli.rb:81:in `new' /Library/Ruby/Gems/2.0.0/gems/sidekiq-3.3.4/lib/sidekiq/cli.rb:81:in `run' /Library/Ruby/Gems/2.0.0/gems/sidekiq-3.3.4/bin/sidekiq:8:in `' /Library/Ruby/Gems/2.0.0/bin/sidekiq:23:in `load' /Library/Ruby/Gems/2.0.0/bin/sidekiq:23:in ` '
It's mostly likely somehow related with either ZenTest or another testing framework.
In my case, i was adding the ZenTest gem both in the development and test groups of my Gemfile. Moving it away from the development group solved the problem.