What are some JavaScript unit testing and mocking frameworks you have used?

QUnit
jqUnit
Writing JavaScript tests with QUnit and jqUnit

QUnit is the unit testing framework for the jQuery JavaScript framework. The testing framework itself uses the jQuery library, but the tests can be written for any JavaScript and do not require the code to use jQuery.

jqUnit is a modified version of QUnit that adds in the setup, teardown, and assert functions that are more typical of an xUnit framework, and encapsulates everything in one global variable.

The visual interface of the testrunner page is nice, allowing you to drill down and see each assert in every test method. Writing tests is fairly easy, and you can run the test code directly on the testRunner page [8]. This allows for easy and visible DOM testing.

QUnit: MIT or GPL (choose) jqUnit: MIT License

Pros

• Asynchronous support
• Good for DOM testing
• Tests always run sequentially in the order they are added to a suite
• Debug on test page using firebug
• Syntax is similar to JUnit if using jqUnit, but simple to learn if using QUnit

Cons

• Automation would be difficult to implement

YUI Test
TDD With YUI Test

YUI Test is the test framework for Yahoo’s User Interface (YUI) library. It is used by Yahoo to test its own library, and has syntax similar to JUnit.

Like jsUnit, YUI Test comes with its own logging console that can output information, warnings and errors in addition to the results of each test.

YUI also provides the ability to send reports on the results in either JSON or XML format.

YUI Test is BSD licensed.

Pros

• Really good documentation
• Active community
• Regular releases
• Syntax is similar to JUnit (test suites, asserts and setup/teardown)
• Asynchronous support
• Good for DOM testing
• Tests always run sequentially in the order they are added to a suite

Cons

• Automation not trivial to implement, but less difficult than other frameworks

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.

I'm not sure why no one has mentioned JsTestDriver! It has to be the one of the only JavaScript testing tools that actually work like you'd expect them to if you've used unit testing tools in other languages.

Running tests can be done without touching a browser, you can integrate it with IDE's, and you can integrate it with Continuous integration systems... Oh, and it's fast, and can run tests in multiple browsers at the same time.

You can also use other testing frameworks like YUITest with it, making it even better.