Unit Testing Basics Edit Page


Unit tests are generally used to test a small piece of code and ensure that it is doing what was intended. Unlike acceptance tests, they are narrow in scope and do not require the Ember application to be running.

As it is the basic object type in Ember, being able to test a simple Ember.Object sets the foundation for testing more specific parts of your Ember application such as controllers, components, etc. Testing an Ember.Object is as simple as creating an instance of the object, setting its state, and running assertions against the object. By way of example lets look at a few common cases.

Testing Computed Properties

Let's start by looking at an object that has a computedFoo computed property based on a foo property.

app/models/some-thing.js
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export default Ember.Object.extend({
  foo: 'bar',

  computedFoo: function() {
    return 'computed ' + this.get('foo');
  }.property('foo')
});

Within the test we'll create an instance, update the foo property (which should trigger the computed property), and assert that the logic in our computed property is working correctly.

tests/unit/models/some-thing-test.js
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import SomeThing from '<your-app-name>/models/some-thing';

moduleFor('model:some-thing', 'Unit: some-thing');

test('computedFoo correctly concats foo', function(assert) {
  var someThing = SomeThing.create({});

  someThing.set('foo', 'baz');

  assert.equal(someThing.get('computedFoo'), 'computed baz');
});

See that we have used moduleFor one of the several unit-test helpers provided by Ember-Qunit.

Testing Object Methods

Next let's look at testing logic found within an object's method. In this case the testMethod method alters some internal state of the object (by updating the foo property).

app/models/some-thing.js
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export default Ember.Object.extend({
  foo: 'bar',
  testMethod: function() {
    this.set('foo', 'baz');
  }
});

To test it, we create an instance of our class SomeThing as defined above, call the testMethod method and assert that the internal state is correct as a result of the method call.

tests/unit/models/some-thing-test.js
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import SomeThing from '<your-app-name>/models/some-thing';

moduleFor('model:some-thing', 'Unit: some-thing');

test('calling testMethod updated foo', function(assert) {
  var someThing = SomeThing.create({});

  someThing.testMethod();

  assert.equal(someThing.get('foo'), 'baz');
});

In the event the object's method returns a value you can simply assert that the return value is calculated correctly. Suppose our object has a calc method that returns a value based on some internal state.

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export default Ember.Object.extend({
  count: 0,
  calc: function() {
    this.incrementProperty('count');
    return 'count: ' + this.get('count');
  }
});

The test would call the calc method and assert it gets back the correct value.

tests/unit/models/some-thing-test.js
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import SomeThing from '<your-app-name>/models/some-thing';

moduleFor('model:some-thing', 'Unit: some-thing');

test('calc returns incremented count', function(assert) {
  var someThing = SomeThing.create({});
  assert.equal(someThing.calc(), 'count: 1');
  assert.equal(someThing.calc(), 'count: 2');
});

Testing Observers

Suppose we have an object that has a property and a method observing that property.

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export default Ember.Object.extend({
  foo: 'bar',
  other: 'no',
  doSomething: function(){
    this.set('other', 'yes');
  }.observes('foo')
});

In order to test the doSomething method we create an instance of SomeThing, update the observed property (foo), and assert that the expected effects are present.

tests/unit/models/some-thing-test.js
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import SomeThing from '<your-app-name>/models/some-thing';

moduleFor('model:some-thing', 'Unit: some-thing');

test('doSomething observer sets other prop', function() {
  var someThing = App.SomeThing.create();
  someThing.set('foo', 'baz');
  equal(someThing.get('other'), 'yes');
});