Test-Driving JavaScript Applications



Venkat Subramaniam
ISBN-13: 978-1680501742

I wanted to start this review simply with “Wow! Just wow!”, but that’s not really going to cut it. It’s true to say that when I first learned that there was going to be a book published called “Test-Driving JavaScript Applications” I was sure it was going to be the book I had been waiting for since at least late 2007 when I was forced to write JavaScript in production for the first time. It’s publication date was pushed back and back, so it really felt like I was being made to wait. However, I wasn’t disappointed and this book was everything I hoped it would be and more.

We all know JavaScript is evil, right? Why is it evil? It’s the lack of a decent type system, the forgiving nature of the compilers and an inability to write meaningful unit tests, especially for the UI (User Interface). It’s difficult to do a huge amount about the first two points, but now JavaScript can be meaningfully unit tested, even in the UI context, with Karma, Mocha and Chai. Test coverage can be measured with Istanbul and System Tests (referred to by Subramanian as Integration Tests – this is my one bugbear with the book) written with Protractor. All of this is described in Test-Driving Java Applications.

I think it’s important to read all of part 1, Creating Automated Tests. The chapters cover everything you need to know to get started writing unit tests for both server side code and UI code, how to test asynchronous code (very important in JavaScript) and how to replace dependencies with test doubles such as fakes, stubs and spies. It’s all demonstrated with a completely test first approach with excellent commentary about how this leads to good design.

I cherry picked from part 2, Real-World Automation Testing. I was only really interested in how to write automated tests for the DOM and JQuery and how to write ‘Integration’ tests. Other chapters included how to write tests for Node.js, Express and two versions of AngularJS. The DOM and JQuery chapter was excellent showing me exactly how to take advantage of test doubles to write fully tested JavaScript without having to fire up a browser, resulting in something I can make immediate use of.

The Integrate and Test End-to-End chapter, which describes how to use Protractor, was almost enough to encourage me to abandon Java (Selenium) for System Tests and move to JavaScript. However, while looking at the latest version of Selenium, there are some other things I want to investigate first.

The final chapter, Test-Drive Your Apps is the equivalent of Pink Floyd playing Run Like Hell at the end after Comfortably Numb. It’s still good, but is really there to help you wind down from the climax and could just as easily have been omitted, but it would feel a bit odd if it was.

If there was one more thing I could get from this book it would be how to send test and coverage results to SonarQube.

If you want to use JavaScript, intend to use JavaScript or are forced to use JavaScript, get this book and automated the testing of your JavaScript.


Originally published at paulgrenyer.bologspot.com

Words by Paul Grenyer

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