Clojure database unit testing / mocking

I just recently started working on a database-heavy Clojure application and am attempting to get some unit tests in place. Ideally, I'd like to avoid actually hitting a real database by mocking things out.

Here's an example of a simple test:

test-core.clj

(deftest core-test
  (is (> (count (fn-under-test "foo")) 0)))

core.clj

(defn fn-under-test [slug]
  (db/query "select * from %1" slug))

db.clj

(defn query [q & args]
  (sql/with-connection db
    (sql/with-query-results res
      [(clause q args)]
      (doall res))))

My question: is there a way, from within test-core.clj, to bind a custom function to 'db/query' such that core.clj will use it, as opposed to the definition within db.clj?

Thanks!