Add tests for comment (#819)

Author: dgr

test/clojure/core_test/comment.cljc

@@ -0,0 +1,10 @@
+(ns clojure.core-test.comment
+  (:require [clojure.test :as t :refer [are deftest is testing]]
+            [clojure.core-test.portability #?(:cljs :refer-macros :default :refer) [when-var-exists]]))
+
+(when-var-exists comment
+  (deftest test-comment
+    (is (nil? (comment)))
+    (is (nil? (comment 1)))
+    (is (nil? (comment nil)))
+    (is (nil? (comment (throw (ex-info "Bad things!!!" {:foo :bar})))))))