Special thank you for Channel 9 and @skimedic for sharing his unit testing knowledge.
XUnit leverage some of the new features to help developers write cleaner test, as tests should be kept clean and treated as first-class citizens.

• NUnit was not fully compatible with .NET Core 2 at the time
• xUnit is aimed at improving test isolation and trying to codify a set of rules to establish a testing standard.
• xUnit Fact and Theory attributes are extensible, so you can implement your own testing functionality.xUnit doesn’t use Test Lists and .vsmdi files to keep track of your tests.
• Microsoft is using xUnit internally, one of its creators is from Microsoft. xUnit was also created by one of the original authors of NUnit.
• Side-by-side Performance Comparison of testing frameworks can be found here https://blogs.msdn.microsoft.com/visualstudio/2017/11/16/test-experience-improvements/

Where to get it and how to add it to your projects (2 ways)

* Use Nuget to add xunit as well as the runner * Add New Project – .NET Core xUnit Test Project

• It does work with live unit testing
• Add Fact attribute on a method to mark it as a test
• Use Theory and InlineData as mechanism to pass data into the test
• Theory attribute to mark a method as a test and setup incoming parameters (2 approaches InlineData and MemberData)
• [InlineData(1,2,3)
• approach to pass data into the test method (add additional InlineData attributes for multiple runs of same test)
• MemberData(nameof(IEnumerable<object>
• In the example below we are using a method to return data to be used (however this method could also read data from other files such as text or excel to be returned)
• approach to pass data into the test method
• xUnit runs it’s tests in parallel to take advantage of today’s processors
• tests within one class are run serial
• tests in multiple classes are run parallel
• can be disabled by creating a test collection (add attribute Collection({name}), and all within the same collection will be run serial
• in order to test that an exception is thrown
• Assert.Throws<InvalidOperationException>(() => ThrowAnError());
• Setup/Teardown
• There are no Setup and Teardown attributes, this is done using the test class’ constructor and an IDisposable. This encourages developers to write cleaner tests.
• use constructor in place of Setup attributes to prepare tests
• now use IDisposable to replace teardown i.e. public class ATestClass : IDisposable public void Dispose() {    //something here to clean up }
• for input/output there exists ITestOutputHelper as shown below to output log

Notes

• Works in .net core and .net framework
• TODO: Read up on Live Unit Testing https://docs.microsoft.com/en-us/visualstudio/test/live-unit-testing?view=vs-2017

References:

https://xunit.github.io/docs/why-did-we-build-xunit-1.0.html https://dev.to/hatsrumandcode/net-core-2-why-xunit-and-not-nunit-or-mstest--aei https://channel9.msdn.com/Shows/Visual-Studio-Toolbox/Unit-Testing-xUnit https://xunit.github.io/