unit testing - Why do I need a mocking framework for my unittests?

Question

Recently there has been quite some hype around all the different mocking frameworks in the .NET world. I still haven't quite grasped what is so great about them. It doesn't seem to be to hard to write the mocking objects I need myself. Especially with the help of Visual Studio I quickly can write a class that implements the interface I want to mock (it auto-generates almost everything for me) and then write an implementation for the method(s) I need for my test. Done! Why going through the hassle of understanding a mocking framework for the sole purpose of saving a few lines of code. Or is a mocking framework not only about saving lines of code?

question from:https://stackoverflow.com/questions/300177/why-do-i-need-a-mocking-framework-for-my-unittests

Answer 1

Once I finally got the hang of mock objects, I realized that they're essential for unit testing for the same reason that double blind testing or control groups are essential for scientific trials: they isolate what you're actually testing.

If you're testing a class which has quite a bit of interaction via other interfaces, you not only save the lines of code on having to mock each and every interface, but you also gain the ability to do things like "throw an exception if an unexpected method is called" or "exception if these methods are called out of order". You can get remarkably sophisticated with mock frameworks, and though I'll quickly admit there's a large learning curve, when you get up to speed they'll help make your unit tests more thorough without being bloated.