Replace method by sinon.stub for testing

sinon_stub.coffee

sinon = require 'sinon'
MongooseModel = require 'mongoosemodeldefinition'

describe 'when the mongoose document failed to save', ()->
  stub = null
  before (done)->
    origSave = MongooseModel.prototype.save
    createCount = 0
    stub = sinon.stub MongooseModel.prototype, 'save', (cb)->
      createCount += 1
      if createCount > 3
        return cb new Error 'Cannot create greater than 3 documents'
      origSave.apply this, arguments
    do done
  after (done)->
    stub.restore()
    do done

  it '(write test...)'