VS2010, Resharper 6.0, xUnit contrib revision f0a427327dca.
- Create a project with references to both Xunit and NUnit.
- Create NUnit test, marked with [Test] attribute
- Run this test.
- Change its attribute from [Test] to [Fact], so that now it becomes Xunit test.
You get exception “Object reference not set to an instance of an object".
Reason: look at XunitTestProvider.cs, method GetOrCreateTestClass, line 159. Here you get IUnitTestElement, but in that case it is not XunitTestClassElement, it is NUnitTestFixtureElement. Probably, this is caused by some bug in ReSharper's UnitTestManager.
Unfortunately, as R# 6.0 is already released this bug won't be fixed. Anyway, in XunitPsiFileExplorer, method ProcessTestClass, line 126, you should probably check that testElement is not null, otherwise you get this exception.
I would suggest you to include this scenario into test suite for integration with R# 6.1. By the way, R# has just opened EAP for 6.1, so if you have any integration problems due to inconsistency at R# side, please, contact their team as soon as possible.
JetBrains dotCover developer.