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Now, it's time to make the web page dynamic — with AngularJS. We will also add a test that verifies the code for the controller we are going to add.

There are many ways to structure the code for an application. For AngularJS applications, we encourage the use of the Model-View-Controller (MVC) design pattern to decouple the code and separate concerns. With that in mind, let's use a little AngularJS and JavaScript to add models, views, and controllers to our app.

- The list of three phones is now generated dynamically from data

## View and Template

In AngularJS, the view is a projection of the model through the HTML template. This means that whenever the model changes, AngularJS refreshes the appropriate binding points, which updates the view.

The view is constructed by AngularJS from this template.

`app/index.html`:

    <html ng-app="phonecatApp">
    <head>
      ...
      <script src="lib/angular/angular.js"></script>
      <script src="app.js"></script>
    </head>
    <body ng-controller="PhoneListController">

      <ul>
        <li ng-repeat="phone in phones">
          <span>{{phone.name}}</span>
          <p>{{phone.snippet}}</p>
        </li>
      </ul>

    </body>
    </html>

We replaced the hard-coded phone list with the ngRepeat directive and two AngularJS expressions:

- The `ng-repeat="phone in phones"` attribute on the `<li>` tag is an AngularJS repeater directive. The repeater tells AngularJS to create a `<li>` element for each phone in the list, using the `<li>` tag as the template.
- The expressions wrapped in curly braces (`{{phone.name}}` and `{{phone.snippet}}`) will be replaced by the values of the expressions.

We have also added a new directive, called ngController, which attaches a `PhoneListController` controller to the `<body>` tag. At this point:

- `PhoneListController` is in charge of the DOM sub-tree under (and including) the `<body>` element.
- The expressions in curly braces (`{{phone.name}}` and `{{phone.snippet}}`) denote bindings, which are referring to our application model, which is set up in our `PhoneListController` controller.

Note: We have specified an AngularJS Module to load using `ng-app="phonecatApp"`, where `phonecatApp` is the name of our module. This module will contain the `PhoneListController`.

## Model and Controller

The data model (a simple array of phones in object literal notation) is now instantiated within the `PhoneListController` controller. The controller is simply a constructor function that takes a `$scope` parameter:

`app/app.js`:

    // Define the `phonecatApp` module
    var phonecatApp = angular.module('phonecatApp', []);

    // Define the `PhoneListController` controller on the `phonecatApp` module
    phonecatApp.controller('PhoneListController', function PhoneListController($scope) {
      $scope.phones = [
        {
          name: 'Nexus S',
          snippet: 'Fast just got faster with Nexus S.'
        }, {
          name: 'Motorola XOOM™ with Wi-Fi',
          snippet: 'The Next, Next Generation tablet.'
        }, {
          name: 'MOTOROLA XOOM™',
          snippet: 'The Next, Next Generation tablet.'
        }
      ];
    });

Here we declared a controller called `PhoneListController` and registered it in an AngularJS module, `phonecatApp`. Notice that our `ngApp` directive (on the `<html>` tag) now specifies the `phonecatApp` module name as the module to load when bootstrapping the application.

Although the controller is not yet doing very much, it plays a crucial role. By providing context for our data model, the controller allows us to establish data-binding between the model and the view. We connected the dots between the presentation, data, and logic components as follows:

- The ngController directive, located on the `<body>` tag, references the name of our controller, `PhoneListController` (located in the JavaScript file `app.js`).

- The `PhoneListController` controller attaches the phone data to the `$scope` that was injected into our controller function. This scope is a prototypal descendant of the root scope that was created when the application was defined. This controller scope is available to all bindings located within the `<body ng-controller="PhoneListController">` tag.

### Scope

The concept of a scope in AngularJS is crucial. A scope can be seen as the glue which allows the template, model, and controller to work together. AngularJS uses scopes, along with the information contained in the template, data model, and controller, to keep models and views separate, but in sync. Any changes made to the model are reflected in the view; any changes that occur in the view are reflected in the model.

To learn more about AngularJS scopes, see the AngularJS scope documentation.

AngularJS scopes prototypically inherit from their parent scope, all the way up to the root scope of the application. As a result, assigning values directly on the scope makes it easy to share data across different parts of the page and create interactive applications. While this approach works for prototypes and smaller applications, it quickly leads to tight coupling and difficulty to reason about changes in our data model.

In the next step, we will learn how to better organize our code, by "packaging" related pieces of application and presentation logic into isolated, reusable entities, called components.

## Testing

### Testing Controllers

The "AngularJS way" of separating the controller from the view makes it easy to test code as it is being developed. In the section "Model and Controller" we have registered our controller via a constructor function on the `phonecatApp` module.

In tests, we use an AngularJS service, `$controller`, which will retrieve a controller by name. It also takes a second argument - a map of dependencies that should be injected.

The following test instantiates `PhoneListController` with a mock scope object, and verifies that the phones array property on the scope contains three records.

This example demonstrates how easy it is to create a unit test for code in AngularJS. Since testing is such a critical part of software development, we make it easy to create tests in AngularJS so that developers are encouraged to write them.

`app/app.spec.js`:

    describe('PhoneListController', function() {

      beforeEach(module('phonecatApp'));

      it('should create a `phones` model with 3 phones', inject(function($controller) {
        var scope = {};
        var ctrl = $controller('PhoneListController', {$scope: scope});

        expect(scope.phones.length).toBe(3);
      }));

    });

- Before each test we tell AngularJS to load the `phonecatApp` module.
- We ask AngularJS to `inject` the `$controller` service into our test function.
- We use `$controller` to create an instance of the `PhoneListController`.
- With this instance, we verify that the phones array property on the scope contains three records.

A note on file naming:

As already mentioned in the introduction, the unit test files (specs) are kept side-by-side with the application code. We name our specs after the file containing the code to be tested plus a specific suffix to distinguish them from files containing application code. Note that test files are still plain JavaScript files, so they have a `.js` file extension.

In this tutorial, we are using the `.spec` suffix. So the test file corresponding to `something.js` would be called `something.spec.js`. (Another common convention is to use a `_spec` or `_test` suffix.)

### Writing and Running Tests

Many AngularJS developers prefer the syntax of Jasmine's Behavior-Driven Development (BDD) framework, when writing tests. Although AngularJS does not require you to use Jasmine, we wrote all of the tests in this tutorial in Jasmine v2.4. You can learn about Jasmine on the Jasmine home page and at the Jasmine docs.

The angular-seed project is pre-configured to run unit tests using Karma, but you will need to ensure that Karma and its necessary plugins are installed. You can do this by running `npm install`.

To run the tests, and then watch the files for changes execute: `npm test`

- Karma will start new instances of Chrome and Firefox browsers automatically. Just ignore them and let them run in the background. Karma will use these browsers for test execution.

- If you only have one of the browsers installed on your machine (either Chrome or Firefox), make sure to update the karma configuration file (`karma.conf.js`), before running the test. Locate the configuration file in the root directory and update the `browsers` property.

  E.g. if you only have Chrome installed:

        ...
        browsers: ['Chrome'],
        ...

- You should see the following or similar output in the terminal:

        INFO [karma]: Karma server started at http://localhost:9876/
        INFO [launcher]: Starting browser Chrome
        INFO [Chrome 49.0]: Connected on socket ... with id ...
        Chrome 49.0: Executed 1 of 1 SUCCESS (0.05 secs / 0.04 secs)

  Yay! The test passed! Or not...

- To rerun the tests, just change any of the source or test `.js` files. Karma will notice the change and will rerun the tests for you. Now isn't that sweet?

Make sure you don't minimize the browser that Karma opened. On some OS, memory assigned to a minimized browser is limited, which results in your karma tests running extremely slow.

## Experiments

- Add another binding to `index.html`. For example:

      <p>Total number of phones: {{phones.length}}</p>

- Create a new model property in the controller and bind to it from the template. For example:

      $scope.name = 'world';

  Then add a new binding to `index.html`:

      <p>Hello, {{name}}!</p>

  Refresh your browser and verify that it says 'Hello, world!'.

- Update the unit test for the controller in `app/app.spec.js` to reflect the previous change. For example by adding:

      expect(scope.name).toBe('world');

- Create a repeater in `index.html` that constructs a simple table:

      <table>
        <tr><th>Row number</th></tr>
        <tr ng-repeat="i in [0, 1, 2, 3, 4, 5, 6, 7]"><td>{{i}}</td></tr>
      </table>

  Now, make the list 1-based by incrementing `i` by one in the binding:

      <table>
        <tr><th>Row number</th></tr>
        <tr ng-repeat="i in [0, 1, 2, 3, 4, 5, 6, 7]"><td>{{i+1}}</td></tr>
      </table>

  Extra points: Try and make an 8x8 table using an additional `ng-repeat`.

- Make the unit test fail by changing `expect(scope.phones.length).toBe(3)` to instead use `toBe(4)`.

## Summary

We now have a dynamic application which separates models, views, and controllers, and we are testing as we go. Let's go to step 3 to learn how to improve our application's architecture, by utilizing components.