Add unit test for Card dashboard_count

test/metabase/models/card_test.clj

+(ns metabase.models.card-test
+  (:require [expectations :refer :all]
+            (metabase.api [card-test :refer [post-card]]
+                          [dash-test :refer [create-dash]])
+            [metabase.db :refer [ins]]
+            (metabase.models [card :refer [Card]]
+                             [dashboard-card :refer [DashboardCard]])
+            [metabase.test.util :refer [random-name]]))
+
+;; Check that the :dashboard_count delay returns the correct count of Dashboards a Card is in
+(expect [0 1 2]
+  (let [{card-id :id}       (post-card (random-name))
+        get-dashboard-count (fn [] @(:dashboard_count (Card card-id)))]
+
+    [(get-dashboard-count)
+     (do (ins DashboardCard :card_id card-id, :dashboard_id (:id (create-dash (random-name))))
+         (get-dashboard-count))
+     (do (ins DashboardCard :card_id card-id, :dashboard_id (:id (create-dash (random-name))))
+         (get-dashboard-count))]))