When comparing NUnit vs xUnit.NET, the Slant community recommends xUnit.NET for most people. In the question“What are the best unit testing frameworks for .NET?” xUnit.NET is ranked 1st while NUnit is ranked 2nd. The most important reason people chose xUnit.NET is:
xUnit.NET has an impressive [list](http://www.bricelam.net/2012/04/xunitnet-extensibility.html) of extensions which other testing frameworks are lacking.
Ranked in these QuestionsQuestion Ranking
Pro Excellent availability of learning resources
Due to it's popularity and active development, plenty of learning resources (such as detailed documentation and various tutorials) exist for learning NUnit.
Pro Widely used
NUnit is one of the most popular testing frameworks for .NET. Other than giving a certain sense of security in the continuation of the project, it also means that there are a lot of third-party resources, guides and tutorials available for NUnit.
Pro Built-in fluent Assertions
It has more readable Assertions out of the box like Assert.That(myClass.MyMethod(null), Throws.ArgumentNullException.With.Message.Contains("param");
NUnit also has good tutorials in using the variants for parameterized tests: e.g. its easy to find an example how to correctly use [TestCaseSource(typeof(myTesCaseEnumerator))].
xUnit.NET has an impressive list of extensions which other testing frameworks are lacking.
Pro Supported and used by Microsoft itself
.NET Core area etc.
Pro More intuitive than other testing frameworks
xUnit.NET uses intuitive terminology and is frequently updated to be more lean and user-friendly.
Con Slow to adapt
NUnit is developed slowly; some developers complain that it is no longer able to keep up with new testing approaches.
Con Lack of documentation
Compared to MSTest and NUnit, xUnit.NET lacks documentation.
Con .NET 4.5+ only
Isn't available prior to .NET 4.5.
(As of today 2018, this isn't really a disadvantage)