Clojurians Log v2

Hi, I have a unit test where I'm trying to swap a state with a mock (of a class). However, this state doesn't get swapped and retains its original value.

(use-fixtures
  :once
  (fn [f]
    (-> (mount/only #{#'http-server.config/env
                      #'http-server.generator.core/generator
                      #'http-server.db.core/*db*
                      #'http-server.handler/app})
        (mount/swap-states {#'http-server.generator.core/generator {:start #(MockGenerator.)}})
        mount/start)
    (f)
    (mount/stop)))

Any idea what's wrong with this code?