Unit test computed property on an Ember controller - unit-testing

Question

The code from my controllers/cart.js:
export default Ember.Controller.extend({
cartTotal: Ember.computed('model.#each.subTotal', function() {
return this.model.reduce(function(subTotal, product) {
var total = subTotal + product.get('subTotal');
return total;
}, 0);
})
)};
This computed property loops over all the elements in the model, adding all the values of the subTotal property, returning a cart total.
cart-test.js
import { moduleFor, test } from 'ember-qunit';
import Ember from 'ember';
moduleFor('controller:cart', {
// Specify the other units that are required for this test.
// needs: ['controller:foo']
});
test('it exists', function(assert) {
var controller = this.subject();
assert.ok(controller);
});
test('cartTotal function exists', function(assert) {
var controller = this.subject();
assert.equal(controller.get('cartTotal'), 30, 'The cart total function exists');
});
The test fails with TypeError: Cannot read property 'reduce' of null because it obviously doesn't have a model to loop over.
How can I mock the dependencies of the cartTotal computed property to make the test pass?
Thanks!

Answer 1

Something along these lines maybe?
import { moduleFor, test } from 'ember-qunit';
import Ember from 'ember';
var products = [
Ember.Object.create({ name: 'shoe', subTotal: 10 }),
Ember.Object.create({ name: 'shirt', subTotal: 20 })];
var model = Ember.ArrayProxy.create({
content: Ember.A(products)
});
moduleFor('controller:cart', {
beforeEach() {
this.controller = this.subject();
}
});
test('cartTotal', function(assert) {
this.controller.set('model', model);
assert.equal(this.controller.get('cartTotal'), 30, 'The cart total function exists');
});

Answer 2

One way to deal with this would be to stub the model in the beforeEach hook:
var sampleModel = [ // sample data that follows your actual model structure ]
moduleFor('controller:cart', {
beforeEach() {
this.controller = this.subject(); // allows you to access it in the tests without having to redefine it each time
this.controller.set('model', sampleModel);
}
});