R# does not recognize NUnit TestFixture attribute

R# is not recognizing NUnit attribute [TestFixture] or [Test] or any other I guess.

This is my first time creating a C# test project. I'm new to .Net and R# so not sure if I'm doing something wrong here or it's actually a bug.

1. Create C# class library targeting .net framework 4.7.1

2. Using nuget manager UI, install nunit(3.10.1).

3. Create a public class with [TestFixture] attribute attached.

4. R# keeps telling me to import NUnit.Framework.Internal.

5. If I do import that, it then says TestFixture has 2 parameters not 0

What is happening?? Strangely running the test works fine, but that popup doesn't go away and it's really annoying.