Unit Testing Ionic Apps Pt 2: Concepts & Project Structure

Jasmine

Jasmine is a BDD (behavior driven development) testing framework that can be used to write JavaScript unit tests and is currently the most popular framework choice for testing angular components. In a nutshell it helps us to create suites of tests that each state a behavior we expect to occur in our program’s logic for it to run correctly. You’ll often see Jasmine test descriptions that state thing’s like ‘it should’ do this, ‘it can’ do that, ‘it cant do that’, etc each describing what a small piece of logic in our program does.

Jasmine concepts and terminology

• Suite: a group of specs, contained within a ‘describe block’
• Spec: a function block that contains one or more test expectations, contained within an ‘it block’
• Matchers: functions that will be used to validate test expectations, these can compare values or objects in order to assert an expected result
• Spies: mock stand-in functions that can be used to validate logic, you can check a spy to see if it’s been called, not been called, called one or more times, etc.

Below is a small code snippet containing the obligatory ‘add 2 numbers’ test to illustrate a super simple example of a suite containing one spec that is uses a matcher to assert an expectation.

describe('Simple math tests', function() {
  it('Should add 2 numbers', function() {
   var calculator = new Calculator();
   expect(calculator.add(2, 2)).toBe(4);
  });
 });

In more realistic coding scenarios we’ll also need to use spies which allow us to provide mock implementations that return results to setup particular test expectations and also let us know if a given function has been called or not.
There are several ways to utilize spies with Jasmine including:
SpyOn an Existing Object
To spy on an object, is to create a stand-in for particular function in order to assert whether or not it has been called and also creates opportunity to arrange for a particular results to be returned in order to facilitate a test sceanrio. It’s important as well that that this stand-in function is called instead of the real code so that our test is isolated from interacting with other systems through network requests, database requests, file io, etc.
In the example below I’m creating a stand-in function called ‘createAccount’ that will be called and then testing that our manager object has called that function when its ‘addUser’ function is called:
Note: if instead of just calling the stand-in function that does nothing you really need the underlying function to be called as well to complete your test scenario you can call spyOn(…).andCallThrough() which will execute both the stand-in and the real function.

describe('User account creation tests', function() {
    it('Should create a new user account', function() {
      var accountService = new AccountService();
      var accountManager = new AccountManager(accountService);
      spyOn(accountService, 'createAccount');
      accountManager.addUser('John', 'Doe');
      expect(accountService.createAccount).toHaveBeenCalled();
    });
    .
    .
    .
  });

Create a Spy Object
Another facility Jasmine provides is the ability to create completely fake stub objects that can do absolutely nothing, or can provide a fake test stub implementation.

describe('User account creation tests', function() {
    it('Should create a new user account', function() {
      var accountService = jasmine.createSpyObj('AccountService', ['userExists', 'createAccount']);
      var accountManager = new AccountManager(accountService);
      accountService.userExists.and.callFake(function(){
        return true;
      });
      spyOn(accountService, 'createAccount')
      expect(accountService.createAccount).not.toHaveBeenCalled();
    });
    .
    .
    .
  });

Use a Spy to Arrange an Expectation
Either by spying on or creating a spy object we can also return a specific result that is needed in order to test a specific scenario, in the example below I’m returning a result from a spy object stub function to say ‘the user name already exists, so the account should not have been created’:

describe('User account creation tests', function() {
      it('Should not create a new user account if the user already exists', function() {
        var accountService = new AccountService();
        var accountManager = new AccountManager(accountService);
        spyOn(accountService, 'createAccount');
        spyOn(accountService, 'userExists').and.returnValue(true);
        accountManager.addUser('John', 'Doe');
        expect(accountService.createAccount).not.toHaveBeenCalled();
      });
    });

Unit Test File Structure

File structure is a very important part of creating a well organized and maintainable software project. How unit tests are woven into the code is no exception and there are a couple of obvious ways to do so:

• Add all your tests in a test directory
• Add your tests along side the code you are testing

The best way I’ve found is a way I’d read about where you use the .spec.js naming convention, adding your tests right along side the components they are testing. This makes it really easy to find unit tests for a given component as well as to see what components have or have not had tests written for them.
Example Project Structure

- myApp
  karma.conf.js
 - www
  - app
   - dashboard
       dashboardController.js
       dashboardController.spec.js
       dashboardService.js
       dashboardService.spec.js
       dashboardModule.js
   - login
       loginController.js
       loginController.spec.js
   .
   .
   .

Test Cleanup Cordova Hook

One issue with creating your unit tests along side your production code in an Ionic project is that they will then be copied out to your application build folder along with the production code. Below is an example Cordova hook I’ve written however that will be used to remove .spec.js files from the build output, removing them from app.  Just add a hook file under your project’s hooks -> after_prepare directory and thefollowing hook code will take care of the clean-up:
note: it requires the node ‘del’ package, so be sure to npm install that as well

#!/usr/bin/env node
var del = require('del');
var specFiles = ['platforms/ios/www/app/**/*.spec.js',
'platforms/android/assets/www/app/**/*.spec.js'];
// Output the names of the files we're about to delete on the console for diagnostic puposes
del(specFiles, {dryRun: true})
.then(function (paths) {
  console.log('Spec files to be removed:\n', paths.join('\n'));
});
// Delete the test .spec.js files
del(specFiles).then(function () {
  console.log("Tests have been removed from your build");
});

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