I hope explanations on how to unit test ktor projects are going to be added to the documentation, or even better yet, to the quick start project structure - it's incredibly difficult to dip into ktor without it being easy to unit test 😞
It will depend on how you architect your code. If you are looking for server side testing, I've written a series of articles about Ktor architecture & testing. You can have a look here:
https://medium.com/@math21
Also some other articles about Ktor deployment and monitoring.