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This is an AngularJS-based application derived from the TodoMVC implementation.

Get started

See the visual regression test suite and all test cases.

Launch src/index.html to open the application. Note though that this will not work for file:// access in some browsers.

What is to see here?

AngularJS applications have an ingrained support for the "separation of concerns" principle. As such setting up view tests is pretty simple.

Looking at test/ui/ng_single_active_entry.html you'll see a test case includes

  • the linked CSS,
  • a HTML template,
  • the AngularJS dependency,
  • a mocked out controller and
  • the application bootstrap helper.

The real controller, the application object or any persistance layer is not needed in the tests.

Modular HTML

The application consists of different partial templates that represent a component each. A template can easily be included using

<ng-include src="'templates/MY_TEMPLATE.html'"></ng-include>

This allows the test cases to include production code for HTML (CSS and JS are naturally easy to link in). Also, this helps structure the HTML into small components that can be tested independently.

There is one issue with template includes: paths in AngularJS' includes are not relative to the including HTML file (violating the pattern defined by CSS), but relative to the outer document running the application. Thus a cascaded of template partials is difficult to include. One solution can be seen in test/ui/ng_initial_view.html. Here the partials that we do not want to test are "mocked out" using an empty template:

<script type="text/ng-template" id="templates/list.html"></script>

Dynamic view

Most views only become completly rendered after some JavaScript code has run manipulating the view state. Triggering this in tests is straightforward with Angular.

Test case test/ui/ng_single_active_entry.html shows a mocked controller manipulating the injected $scope object, that is then reflected in the view

function TodoCtrl($scope) {
    $scope.todos = [{
        title: 'an active entry',
        completed: false

Setting up a production-like HTML tree

The TodoMVC application was not designed with independent components in mind. Thus testing parts of the components is not straightforward. For example, the correct styling is only applied if the TODO item list is included in a #main section again included in #todoapp. The test case is careful to mimic the tree as it exists in the live application.

<section id="todoapp" ng-controller="TodoCtrl">
    <section id="main">
        <ng-include src="'src/templates/list.html'"></ng-include>

In a clearly-separated component such setup would probably not be needed.

AngularJS bits

The test cases create an alternative application using their own controller. This allows for writing slim test cases keeping out any code that we do not want to test.

The application is bootstrapped by calling


while the controller is either referenced in the included template, or is manually invoked inside the test

<section id="todoapp" ng-controller="TodoCtrl">

One special treatment is needed in addition, as AngularJS by default catches errors thrown in the application without reporting them back. To allow CSS Critic to inform you about errors in your setup, the test/ui/angular_testhelper.js makes sure to rethrow errors otherwise hidden away.

Wiring together

The browsers limit the paths accessible out of same-origin restrictions. This makes wiring up the test suite a tiny bit more complicated. Let's look at test/ui/ng_single_active_entry.html for example. While the document sits under test/ui/ the application is found under ../../src/ relativly from there. If we linked like that, Firefox would complain about accessing a restricted path. Instead we apply a small tweak. We create a symbolic link in the test/ui/ directory via

$ ln -s ../../src test/ui/src

from the project's root directory and link to src/ inside the document. This allows us to write the following:

<link rel="stylesheet" href="src/base.css">

If the RegressionRunner.html file is served through a (local) web-server, this will not be an issue whatsoever.