FluentAssertion is not compatible with xUnit.Extensions

I met a weird problem that I found the Resharper Test Runner hangs when I introduced theory test case in my unit test.
After some spikes, I found the problem seems caused by the incompatibility between Fluent Assertion and xUnit.Extension.
It is wired, and there seems to be no quick fix.
So I replace the Fluent Assertion with Should and Should.Fluent, which is a port of ShouldIt.
After that, everything goes well except the syntax between Fluent Assertion and Should Fluent are not compatible with each other, although they’re really similar.
But Should.Fluent doesn’t support something.Should.Be(), it requires something.Should.Be.Equals(), which is really annoying to me.

According to the Fluent’s introduction, Fluent is a direct fork of xUnit. And I’m not sure what’s the impact caused by this.