How to avoid database access performed by type-hinted models in controllers while testing?

I have a PostController which contains the following method:

public function show(Post $post) { /* Stuff */ }

While testing my controllers, is it possible to avoid the database query performed by the Post class?

I tried mocking my Post model at no avail. The approach suggested by Jeffrey here didn't work either: https://gist.github.com/JeffreyWay/4968363

This is not a blocker as I can either use an in-memory SQLite database or, as a last resort, even remove the type-hinted model.

How do you guys workaround this issue?