Hi, thanks for sharing this issue.

Inheriting from Xunit attributes is basically extending the functionality of the Xunit adapter. NCrunch doesn't support this kind of extensibility, as it's impossible for us to predict how people might change the behaviour of Xunit so we have no way to implement the handling around it.

This isn't to say that inheriting from Xunit attributes won't work on NCrunch, rather that we cannot warrant that it will and can't provide help for when it fails. For this particular mechanism I recommend instead just adding a line of code to the top of the test to check for the debugger. If a generic approach is extremely important you might want to look into an AOP enabling system, perhaps an IL weaver (like Fody).