When comparing MSTest vs NUnit, the Slant community recommends NUnit for most people. In the question“What are the best unit testing frameworks for .NET?” NUnit is ranked 2nd while MSTest is ranked 4th.
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Pros
Pro Visual Studios integration
MSTest is fully integrated with Visual Studios and works natively without the need for any plugins.
Pro Better support for integration and system test
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))].
Cons
Con Bad at bridging technologies
MSTest is better suited for only using Microsoft technologies rather than mixed technology environments.
Con Slow to adapt
NUnit is developed slowly; some developers complain that it is no longer able to keep up with new testing approaches.