Question

I’m just getting started with Ember and come across this issue while writing some jasmine tests.

Given I have the following code

App.RecipeController = Ember.Controller.extend
  selectedGrain: null
  amount: null
  recipeGrains: Ember.A()

  totalWeight: (->
    weight = 0
    @get('recipeGrains').forEach (grain) ->
      weight += grain.get('weight')
    weight
  ).property('recipeGrains.@each')

  addGrain: ->
    grain = Ember.Object.create
      name: @get('selectedGrain').get('name')
      weight: parseFloat(@get('amount'))
    @get('recipeGrains').pushObject(grain)
    @set('selectedGrain', null)
    @set('amount', null)

And I write the following test.

describe("Controllers", function() {
  describe("NewRecipeController", function() {
    var controller;

    beforeEach(function() {
      controller = Brewery.NewRecipeController.create();
    });

    it("calculates the correct total weight", function() {
      var grains = controller.get('recipeGrains');
      grains.pushObject(Ember.Object.create({weight: 4.0}));
      grains.pushObject(Ember.Object.create({weight: 3.2}));
      expect(controller.get('totalWeight')).toEqual(7.2);
    });

    it ("adds grains based on its selected grain", function() {
      controller.set('selectedGrain', Ember.Object.create({name: "Wheat"}));
      controller.set('amount', '10.2');
      controller.addGrain();
      expect(controller.get('totalWeight')).toEqual(10.2);
    });
  });
});

I expected that both tests would pass, but instead the second test fails with the message

Expected 17.4 to equal 10.2.

It seems the state of the first test is spilling over the the second test. Can someone more knowledgeable than I pelase explain how Ember handles controller states and why this happens?

Thank you!

Answer 1

The reason why your test fails is the default value initialization @ line 4.

You should either set the initial value in init method in App.RecipeController or passing the value at instance creation:

App.RecipeController = Ember.Controller.extend
  init: ->
    @set 'recipeGrains', Ember.A()

or

controller = Brewery.NewRecipeController.create({ recipeGrains: Ember.A() });

You should have a look to section 6 of this article.