Is it possible to have copilot use my own standards for how it writes unit tests?

I find the most recent combo of VS2022 and copilot have gotten much better at writing unit tests. They have gone from doing 40-50% of the work to perhaps 80%, depending on the complexity of the class (I am using C#)

I use a prompt like "using mstest and moq, write unit tests for this class"

I then modify the results to do a few things the way I like to do them. For example, if the class is using IMapper from Automapper, copilot always mocks IMapper. But I have a factory method I use in tests to use the actual map profiles. So, instead of having:

private Mock<IMapper> _mockMapper;

..

_mockmapper = new Mock<Imapper>();

..

_mockmapper.Setup(blah blah)

I replace it with

private IMapper _mapper;

..

_mapper = MapFactory.Create();

..

Other than including something like "use MapFactory.Create() for IMapper" in the prompt, is there a way to change copilot to always use that in my projects?

Ultimately, I want to do this kind of thing for more than just the above IMapper example. But I don't know where to start. Was hoping there might be a "prompt rules" file I can include in a project with customizations like the above.