Net 4.7.2 is supported by Verify I would rather keep a lower end test than upper, would this be acceptable,

Absolutely, no idea why I didn't use this version. Its a shame as I'd prefer to test the generated code for .NET 461 as its the most different version (Iirc Unsafe.As isn't available.)

the other option is to move the API Tests to a separate test project.
I wanted to get the API tests added and for the moment to avoid breaking changes, I have excluded net 4.6.2 from the API tests and am only checking net 6 and net 8

Which API tests are you talking about, are you talking about all the tests in Refit.Tests? I wasn't aware you'd recently added tests 🤔

I'm also not sure if my generator tests are even using .NET Framework, NET 6.0, NET 8.0 when running. AFAIK refit.Tests\InterfaceStubGenerator uses VerifyCSV2.Testand ReferenceAssemblies to build the given file in the correct version (I think). I don't know how CSharpCompilation.Create chooses which version of .NET to use.

I'm tempted to close this PR and use it for testing a source generator rewrite (if I ever get round to it). Moving the tests from InterfaceStubGenerator isn't the main goal. I was planning on using this project for tests like the following:

public async Task TestRouting()
{
  // fixture adds this method into a blank refit interface file and verifies the output.
  await Fixture.VerifyMethod(
  """
  [Get("/group/{id}/users")]
  Task<List<User>> GroupList([AliasAs("id")] int groupId, [AliasAs("sort")] string sortOrder);
  """);
}