em-rspec is a very simple patch to RSpec 2 that sets up and tears down an EventMachine reactor loop, and runs each example within the context of the loop. It also will wrap each example in a Fiber so you are free to untangle nested callbacks.

gem install em-rspec

require 'em-rspec'

em-rspec extends RSpec in an unobtrusive way that requires no addtional code in your specs to test EM code. e.g.

describe 'em-rspec' do
  it 'executes specs within a reactor loop' do
    EM.reactor_running?.should be_true # This is true
  end
end

As mentioned before, before the spec is run, a reactor loop is setup, and a callback to teardown the loop when your example finishes execution is created. This is an important point to consider because if you do any asynchronous i/o operations, your code will not be tested, because your code will likely have finished execution before the i/o operation is complete. It is an antipattern to actually hit the network in your tests and what you should do is mock out i/o calls to return immediately, e.g. http calls with webmock.

This is how your examples are run with em-rspec:

• Set up reactor loop
• Set callback to tear down reactor loop when spec is finished
• Wrap example in fiber
• Run before each block
• Run example
• Run after each block
• Tear down reactor loop

© 2011 Stevie Graham