How To Unit Test MongoDB with Luminus?

I'm probably missing something simple, but I'm not experienced enough with clojure to understand the error I'm getting.

I have a simple luminus clojure app setup with the Monger library to handle my MongoDB connection. I've added a simple test that should always pass to my tests file.

(testing "create user"
    (let [result (db/create-user "test" "test" "test")]
    (is (true? true))))

This doesn't work however, and throws the following error

java.lang.ClassCastException: mount.core.DerefableState cannot be cast to com.mongodb.DB

I'm assuming this has to do with the test environment not properly setting up the database stuff and failing there. I've done a bit of searching, but nothing helpful has come up and there doesn't appear to be any testing help in the Monger Docs. I know for sure that the above create-user call does work when running in the actual environment.