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Test Driven Development with Javascript



I've had a few opportunities to put my TDD skills to use in this brave new frontier. So I wanted to share what I've learned, what pitfalls to avoid and where the low hanging fruit is.

Why use TDD in Javascript?
We've reached a point where few people can develop an application without there being a web interface included. And now it's not enough to build a website with a few forms and buttons it has to be a "web application" with the detailed user interface and responsiveness we would expect of a desktop application. Javascript is serious business. Clients are not going to compliment you on your stable and fully tested backend if the UI is painful.

When should you not use TDD in Javascript?
Javascript has a strange distinction. It is the most widely used programming language in the world. It is also the most disliked programming language in the world. It can be hard to get programmers to learn Javascript before they dive into writing Javascript. So you cannot expect unit tests in that environment. It may be that your programmers are just copying the latest jquery plugins and performing wonders while writing very little Javascript  If there’s very little Javascript being written then there’s no point trying to automate the testing.

Okay. So do I test in Selenium or Watir?
Wait just a minute now! Those are not unit testing frameworks. They can be great for integration testing to see the behaviour with the DOM and a backend. But TDD requires unit tests that are fast to write and fast to run. I’m going to use Jasmine but there’s lots of other unit test frameworks to pick from and I’ll walk through the ways to run it on a console, through a browser and distributed through many browsers.

Next time
Writing testable javascript and what not to test

This is part of a series I'm writing for Agile+ on Google+ so you can follow as I post them there

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