Using unit tests

Unit tests are used to test smaller chunks of functionality. In this recipe, we'll see an example of this.

How to do it...

In this example, we'll create a simple Ember.Object with a computed property. We'll test this computed property and assert if the value returned is correct or not.

  1. In a new project, create a new first-last.js file in the models folder:
    // app/models/first-last.js

import Ember from 'ember';

export default Ember.Object.extend({
    firstName: 'John',
    lastName: 'Smith',
    fullName: Ember.computed('firstName', 'lastName', function() {
      const firstName = this.get('firstName');
      const lastName= this.get('lastName');
      return `Full Name: ${firstName} ${lastName}`;
    })
});

    In this file, we have two properties, firstName and lastName. The fullName computed property combines these two and returns a full name. If either of these properties change, the computed property will fire.

  2. Create a new unit test that checks Ember.Object and computed property:
    $ ember g model-test first-last

    The model-test unit test generated will create a new test file in the /tests/unit/models directory.

  3. Update the first-last-test.js file with a new unit test that checks to see whether the computed property is returning the correct values:
    // tests/unit/models/first-last-test.js

import { moduleFor, test } from 'ember-qunit';

moduleFor('model:first-last', 'Unit | Model | fullName', {
    unit: true
});

test('check computed property fullName', function(assert) {
    const firstLast= this.subject();
    firstLast.set('firstName','Erik');
    firstLast.set('lastName','Hanchett');
    assert.equal(firstLast.get('fullName'), 'Full Name: Erik Hanchett');
});

    The moduleFor is a unit test helper provided by ember-qunit. This helps us get access to the model that we created for lookup and instantiation. The unit: true property flags the test case as a unit test. As we are using moduleFor, we can instantiate the firstLast object using this.subject(). The test then sets firstName and lastName of the computed properties and does assert to make sure that they are equal.

  4. Run ember server and check the output of the /tests URL:
    How to do it...

    The output shows that the unit tests passed

  5. Update the first-last-test.js file with the wrong value:
    // tests/unit/models/first-last-test.js
…
test('check computed property fullName', function(assert) {
    const firstLast= this.subject();
    firstLast.set('firstName','Erik');
    firstLast.set('lastName','Hanchett');
    assert.equal(firstLast.get('fullName'),'Full Name: Erik wrong');
});

    We updated the code, so now the test will fail because the text does NOT match.

  6. Navigate to the /tests folder and see the output:
    How to do it...

    Now the test fails because the text does not match. You can see this output by navigating to the /tests folder or running ember test from the command line.

How it works...

Unit tests are used to test small pieces of code or functionality. They are another part of the Ember QUnit library. Unit tests can run for virtually anything in your application, including models, components, or controllers.

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