What are some JavaScript unit testing and mocking frameworks you have used?
My main JavaScript framework is jQuery, so I would like my unit test and mocking frameworks to be compatible with that. I'd rather not have to introduce another JavaScript framework.
I am currently using QUnit for unit testing and Jack for mocking, but I am pretty new to the whole unit testing of JavaScript.
Is there a better tool to suggest? What has worked for you?
Answer
I think that Jack is the best mocking framework for JavaScript as of the time of this writing. The main reason is that what's right for JavaScript is not likely what is right for a strongly typed language such as Java.
Many JavaScript mocking frameworks are inspired by Java mock frameworks (such as the excellent JsMockito, for example). But the problem with these is that they require dependency injection, because that's about the only reasonable way to use mocking in Java. But in JavaScript, there are many ways to use mocking, and you are not forced into using dependency injection everywhere.
For example, with JsMockito, you have to make mocks and then pass those mocks into your software-under-test (SUT). The SUT has to directly call the mocks. Therefore, you're forced to code the SUT as a constructor or function that takes in all its dependencies as parameters. (Sometimes, that's a fine way to implement it, but not in every case. The tail is wagging the dog if your mocking framework's design forces your implementation approach.)
In JavaScript, it's very easy to "hijack" any function. Therefore, there are tons of ways to build something such that you can mock parts of it without explicitly injecting its dependencies into it. For example, Jack lets you mock any function, whether it is public or on a local object. From there you can spy on it, stub it, or express expectations on it. The key point is this: once you've mocked a function, any calls to that original function will instead be directed to your mock. In other words, your mocks will still get used even though the original, un-mocked function was called. As a result, you are not forced to inject dependencies, although you certainly can do so in those cases which call for it.
JavaScript is a different language than Java (and C#, etc.). It allows for different implementation idioms. Dependency injection is still one valuable tool in the toolbox in JavaScript, but it is not the only game in town any more. Your mocking framework needs to know and respect that fact. Jack and a couple of others do, but of the ones that do, Jack appears to be the most mature and feature-rich.