Test pop! (#796)

This closes #397.

Author: super7ramp

test/clojure/core_test/pop_bang.cljc

@@ -0,0 +1,35 @@
+(ns clojure.core-test.pop-bang
+  (:require [clojure.test :refer [are deftest is testing]]
+            [clojure.core-test.portability #?(:cljs :refer-macros :default :refer) [when-var-exists]]))
+
+(when-var-exists pop!
+  (deftest test-pop!
+
+    (testing "nominal cases"
+      (are [expected vec] (= expected (persistent! (pop! (transient vec))))
+                          [] [nil]
+                          [] [1]
+                          [1 2] [1 2 3]
+                          [:c :b] [:c :b :a]))
+
+    (testing "cannot pop! empty vector"
+      (is (thrown? #?(:cljs js/Error :default Exception) (pop! (transient [])))))
+
+    (testing "cannot pop! after call to persistent!"
+      (let [t (transient [0 1]), _ (persistent! t)]
+        (is (thrown? #?(:cljs js/Error :cljr Exception :default Error) (pop! t)))))
+
+    (testing "bad shapes"
+      (are [arg] (thrown? #?(:cljs js/Error :default Exception) (pop! arg))
+                 (transient {:a 0})
+                 (transient #{0})
+                 [0]
+                 '(0)
+                 #{0}
+                 (range 3)
+                 true
+                 false
+                 "s"
+                 3.14
+                 42
+                 nil))))