Use SinonJS and Mocha to test async function of multiple callbacks

sinon_mocha_test_async_multi_callbacks.coffee

should = require 'should'
sinon = require 'sinon'

myModule = {}

myModule.asyncMethod = (callback) ->
    timeout = 1000

    setTimeout (->
        process.nextTick ->
            callback null, {
                number: 0
            }
        setTimeout (->
            process.nextTick ->
                callback null, {
                    number: 1
                }  
            setTimeout (->
                process.nextTick ->
                    callback null, {
                        number: 2
                    }    
            ), timeout  
        ), timeout    
    ), timeout

describe 'my module', ->
    describe '#asyncMethod', ->
        it 'should call back 3 times with no error and an object data', (done) ->
            spy = sinon.spy()
            callback = sinon.spy()
            clock = sinon.useFakeTimers()
            
            myModule.asyncMethod (err, data) ->
                callback err, data
                if data.number is 2
                    done()

                    # assertions
                    spy.calledBefore(callback).should.be.true
                    callback.callCount.should.eql 3

                    call0 = callback.getCall 0
                    call0.calledWithExactly(null, {
                        number: 0
                    }).should.be.true

                    call1 = callback.getCall 1
                    call1.calledWithExactly(null, {
                        number: 1
                    }).should.be.true

                    call2 = callback.getCall 2
                    call2.calledWithExactly(null, {
                        number: 2
                    }).should.be.true

            spy()

            clock.tick 3100
            clock.restore()