VS 2013 MSTest vs nUnit vs xUnit

I have listed down the comparisons in two categories:

Framework:

Implementation:

The source of these comparisons

Here is a brief Analysis of the 3 Frameworks and ranked by color.

Legend of the Coloring:

MSTest it is good only because it is simple and integrated into Visual Studio and it comes from Microsoft. Its not flexible enough and not very extensible. But more than just a unit test framework, it also supports Integration tests, Web (load) performance tests. The other 2 are pure Unit Test Frameworks. So I would say MSTest is "Jack of all Trades, Master of none."

NUnit is my choice because its been the best consistently long enough. It is more flexible and simple with very good user base, documentation and community support.

XUnit is least of my choice because it follows a slightly different style and personally I do not see much advantage over NUnit. In some cases you will need to do some refactoring your code to fit into the test cases. But this is just my opinion as there are many who prefers XUnit.

I am biased because I work on NUnit, but the advantage of NUnit or xUnit is that both frameworks offer more functionality like data driven tests, parallel execution and a host of advanced features.

That said, there is nothing wrong with MSTest especially if your team is not very experienced with unit testing. It is well integrated with Visual Studio and with TFS, so adding tests is fairly painless. Both NUnit and xUnit integrate well too, but they may require more setup.

Go ahead and start with MSTest. It is an easy introduction to unit testing. If you start running into some of the limitations of MSTest, then it is a fairly easy migration to NUnit or xUnit. For simple cases, it is just a matter of changing your NuGet packages and then find/replace the attributes.

When it comes to choosing between xUnit and NUnit, both are great choices but each has a different philosophy. NUnit tends to be more flexible and allows for a range of testing styles and can be used for integration tests. It is however flexible enough to allow you to shoot yourself in the foot and allows you to write tests that purists would frown upon. NUnit leaves the choice up to you.

xUnit however tends to be a bit more opinionated and pushes you towards the 'pit of success' with unit testing. In my experience, it is great for green field projects, but it can make testing some poorly architected brown-field projects difficult without refactoring.

In the end, you can't go wrong with any of these test frameworks.

I would like to add one negative aspect of XUnit. It does not have even a basic documentation, nothing beyond "Get Started". No API, nothing.