[bunderbunder]

Microsoft's changing their approach, but it tends to take a long time for the rest of the .NET ecosystem to catch up.

Case in point: Judging by all the .NET code Microsoft has up on GitHub, they've more-or-less completely switched over to xUnit.NET for their testing framework.

Meanwhile, in most Microsoft shops MStest is still considered the best-in-breed option purely by virtue of the fact that Microsoft wrote it. NUnit is a strong counterculture alternative in the same way that espresso drinks are still considered a counterculture beverage in some circles. And nobody has even heard of xUnit.NET.