The Mocha (http://visionmedia.github.io/mocha/) framework supports test suites, specs, and multiple test paradigms. Some of the nifty features offered by Mocha include frontend and backend integration, versatile timeouts, slow test identification, and many different test reporters.

To run Mocha tests in a browser, we just need two files—mocha.js and mocha.css. For version 1.9.0, both these files are available from GitHub at the following locations:

The JavaScript (mocha.js) file contains the library code and the CSS (mocha.css) file provides the styles for the HTML reporter page. With these files in place, we can organize our tests into suites and specs, run our tests, and get a usable report of test results.

Chai (http://chaijs.com/) is a test assertion library that offers an extensive API, support for Behavior-Driven Development (BDD) and Test-Driven Development (TDD) test styles, and a growing plugin ecosystem. BDD and TDD will be introduced in more detail in Chapter 2, Creating a Backbone.js Application Test Plan. In particular, we will use Chai's chainable test functions to write assertions that read very closely to natural language, allowing tests to maximize comprehensibility while minimizing the need for explanatory code comments.

For integration, we need to download a single library file—chai.js. The version (1.7.1) that we want is available at https://raw.github.com/chaijs/chai/1.7.1/chai.js.

Alternatively, the current stable version of Chai can be found at http://chaijs.com/chai.js.

The Sinon.JS library (http://sinonjs.org/) provides a powerful suite of test spies, stubs, and mocks. Spies are functions that analyze and store information about an underlying function and can be used to verify historical behavior of the function under test. Stubs are spies that can replace a function with a different behavior more amenable to testing. Mocks spy on and stub functions as well as verify that certain behavior has occurred during test execution. We will explain these tools in more detail throughout this book.

In practice, Backbone.js applications comprise many different and constantly interacting parts, making our goal of testing isolated program components difficult. A mocking library such as Sinon.JS will allow us to separate testable application behaviors and focus on one thing (for example, a single view or a model) at a time.

Like Chai, we just need a single JavaScript file to use Sinon.JS in our tests. Versioned releases—we will use version 1.7.3—are available at either of the following locations:

Installation of Sinon.JS, along with Mocha and Chai, completes the acquisition phase of our test infrastructure creation.