RSpec::EventMachine

This library provides some extensions to RSpec that make testing EventMachine-based applications easier. It includes functionality for running asynchronous code in tests, and for stubbing out the EventMachine timer methods.

$ gem install rspec-eventmachine

The library includes two main modules: AsyncSteps facilities the writing of tests with async logic, and FakeClock stubs out timer methods.

To keep async tests clean, it helps to implement all the separate logical steps in them as separate functions. Using AsyncSteps, you write a module containing definitions of all your test steps, where each method takes a callback. You then mix this module into your tests, and you can use the methods without callbacks to write terse, flat tests.

require "rspec/em"

MathSteps = RSpec::EM.async_steps do
  def add(x, y, &callback)
    EM.add_timer 0.1 do
      @result = x + y
      callback.call
    end
  end

  def multiply(f, &callback)
    EM.add_timer 0.2 do
      @result = @result * f
      callback.call
    end
  end

  def check_result(n, &callback)
    @result.should == n
    callback.call
  end
end

describe "Math" do
  include MathSteps

  it "adds and multiplies" do
    add 3, 4
    multiply 5
    check_result 35
  end
end

Note that you must put all the logic in the async steps module. The method calls in your before, after and it blocks are really just adding the named methods and arguments to a queue, which AsyncSteps executes sequentially by calling each method when the previous one invokes its callback. AsyncSteps also makes sure that the reactor is running for the duration of each test, and catches and reports any errors or failures that happen during the test.

The FakeClock module lets you freeze time and move it forward by hand, to test code that uses the EventMachine add_timer and add_periodic_timer methods.

require "rspec/em"

describe "Math" do
  include RSpec::EM::FakeClock

  before { clock.stub }
  after { clock.reset }

  it "adds and multiplies" do
    value = 0
    EM.add_timer(1) { value += 3 }
    EM.add_timer(3) { value *= 2 }

    clock.tick(2)
    value.should == 3
    clock.tick(2)
    value.should == 6
  end
end

Copyright (c) 2011-2013 James Coglan

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