Gemfile(5) - A format for describing gem dependencies for Ruby programs

Gemfile(5) - A format for describing gem dependencies for Ruby programs:

# setup adds gems to Ruby's load path Bundler.setup # defaults to all groups require "bundler/setup" # same as Bundler.setup Bundler.setup(:default) # only set up the _default_ group Bundler.setup(:test) # only set up the _test_ group (but `not` _default_) Bundler.setup(:default, :test) # set up the _default_ and _test_ groups, but no others # require requires all of the gems in the specified groups Bundler.require # defaults to just the _default_ group Bundler.require(:default) # identical Bundler.require(:default, :test) # requires the _default_ and _test_ groups Bundler.require(:test) # requires just the _test_ group

Full article: http://gembundler.com/man/gemfile.5.html