Add tests

test/metabase/automagic_dashboards/filters_test.clj

+(ns metabase.automagic-dashboards.filters-test
+  (:require [expectations :refer :all]
+            [metabase.automagic-dashboards.filters :refer :all :as filters]))
+
+;; Replace range with the more specific `:=`.
+(expect
+  [:and [:= [:field-id 2] 42] [:= [:fk-> 1 9] "foo"]]
+  (inject-refinement [:and [:= [:fk-> 1 9] "foo"]
+                            [:and [:> [:field-id 2] 10]
+                                  [:< [:field-id 2] 100]]]
+                     [:= [:field-id 2] 42]))
+
+;; If there's no overlap between filter clauses, just merge using `:and`.
+(expect
+  [:and [:and [:and [:= [:field-id 3] 42] [:= [:fk-> 1 9] "foo"]] [:> [:field-id 2] 10]] [:< [:field-id 2] 100]]
+  (inject-refinement [:and [:= [:fk-> 1 9] "foo"]
+                           [:and [:> [:field-id 2] 10]
+                                 [:< [:field-id 2] 100]]]
+                     [:= [:field-id 3] 42]))