Mocha runs independently from the [assertion library](http://visionmedia.github.io/mocha/#assertions), so you can choose which assertion format works best for you. Mocha most often is run in combination with assertion library [Chai](http://chaijs.com).
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Pro Runs in Node.js and the browser
Mocha has a browser build as well as a node command line program so you can test in client and server side environments.
Pro Write tests with Behavior Driven Development (BDD)
Allows developers to choose their development process. Not only TDD but also BDD.
Pro Makes Asynchronous testing extremely easy
No need to write tricky statements for Async testing. Mocha gives you a
done callback. Place this
done parameter in your callback function, that'll let Mocha know that you've written an asynchronous function.
Pro Integrates really well with NodeJS
The Mocha test framework itself runs on NodeJS, hence it makes everything related to it extremely simple. With Mocha's simple syntax and speed, testing your node.js app just got a whole lot easier.
Pro Custom full color test reporters
Mocha has multiple test reporters built in and you can create your own as well. The test reporters have full color and makes it easy to see if your tests fail or not.
Pro Easy to add support for Generators
Aside from the numerous benefits with generators in your application, You can now also integrate generators into your test suite. By using mocha, all you have to do is enable support for generators.
Pro Supports deferring tests
No need to comment out your entire test case, now that you have Buster, which supports deferring a test so it doesn't actually run, but you get notified that there’s a deferred tests every time you run your test suite.
Pro Flexible; extend it to wrap other test-frameworks
Have your test cases written in another framework, want to use BusterJS to run the tests, then you're in luck. BusterJS can be easily wrapped around other test frameworks. If you need to know how to do it, here's a link that showing just that.
Pro Has support for NodeJS testing.
Working on a NodeJS app? BusterJS can help you Unit test it. This pretty much works just like browser tests, but you need to require Buster.JS in your tests.
Pro You have the option of either running tests headless or via the browser
Don't have time to go through the lengthy process of opening up your browsers? BusterJS gives you the option of performing Headless tests. These are powered by PhantomJS; hence all your testing is done within the command line.
Con Can be intimidating for beginners
While some testing frameworks are complete out of the box, Mocha requires developers to select and set up assertion libraries and mocking utilities. For someone who is just starting to learn how to build tests this can be scary as they will also have to choose which libraries to use and learn them too.
Con No atomic tests
Tests cannot be ran in random order.
Con Has no plugins for major IDE's (Eclipse/IntelliJ) yet.
Do you prefer running your test cases from inside your IDE? well BusterJS will make that a lot difficult for you if not impossible. You'll have to run Buster using the good old way of spawning up a new terminal for running the tests.
Con Currently still in Beta; some of the stuff still has bugs
Time of writing : 31st July 2014