Test descendants (#834)

This closes #236.

Author: super7ramp

test/clojure/core_test/descendants.cljc

@@ -0,0 +1,128 @@
+(ns clojure.core-test.descendants
+  (:require [clojure.test :refer [are deftest is testing use-fixtures]]
+            [clojure.core-test.portability #?(:cljs :refer-macros :default :refer) [when-var-exists]]))
+
+(when-var-exists descendants
+
+  ; Some types for testing descendants by type
+  (defprotocol TestDescendantsProtocol)
+  (defrecord TestDescendantsRecord [] TestDescendantsProtocol)
+  (deftype TestDescendantsType [] TestDescendantsProtocol)
+
+  ; A global hierarchy for testing `descendants tag` and `descendants h tag`
+  (def global-hierarchy [[TestDescendantsRecord ::record]
+                         [::t ::p-1]
+                         [::t ::p-2]
+                         [::p-1 'ns/p-0]
+                         [::p-2 ::root]
+                         ['ns/p-0 ::root]])
+
+  (defn register-global-hierarchy []
+    (doseq [[tag parent] global-hierarchy]
+      (derive tag parent)))
+
+  (defn unregister-global-hierarchy []
+    (doseq [[tag parent] global-hierarchy]
+      (underive tag parent)))
+
+  (defn with-global-hierarchy [tests]
+    (register-global-hierarchy)
+    (tests)
+    (unregister-global-hierarchy))
+
+  (use-fixtures :once with-global-hierarchy)
+
+  ; A hierarchy for testing `descendants h tag`
+  (def datatypes
+    (-> (make-hierarchy)
+        (derive TestDescendantsRecord ::datatype)
+        (derive TestDescendantsType ::datatype)
+        (derive TestDescendantsType ::mutable)))
+
+  ; Another hierarchy for testing `descendants h tag`
+  (def diamond
+    (-> (make-hierarchy)
+        (derive ::a ::root)
+        (derive ::b ::a)
+        (derive ::c ::a)
+        (derive ::d ::b)
+        (derive ::d ::c)))
+
+  (deftest test-descendants
+
+    (testing "descendants tag"
+
+      (testing "returns descendants by relationship globally defined with derive"
+        (are [expected tag] (= expected (descendants tag))
+                            nil ::t
+                            #{::t ::p-1} 'ns/p-0
+                            #{::t ::p-1 ::p-2 'ns/p-0} ::root
+                            #{::t} ::p-2
+                            #{#?(:bb 'clojure.core_test.descendants/TestDescendantsRecord :default TestDescendantsRecord)} ::record))
+
+      (testing "cannot get descendants by type inheritance"
+        (is (nil? (descendants TestDescendantsProtocol)))
+        #?(:cljs    (is (nil? (descendants js/Object)))
+           :default (is (thrown? Exception (descendants Object)))))
+
+      (testing "does not throw on invalid tag"
+        (are [tag] (nil? (descendants tag))
+                   nil
+                   "anything"
+                   42
+                   3.14
+                   true
+                   false
+                   []
+                   {}
+                   #{}
+                   '())))
+
+    (testing "descendants h tag"
+
+      (testing "returns only descendants declared in h, whether the tag is in global hierarchy or not"
+        (are [expected h tag] (= expected (descendants h tag))
+
+                              ; tag in h and not in global hierarchy
+                              nil diamond ::d
+                              #{::d} diamond ::b
+                              #{::b ::c ::d} diamond ::a
+                              #?(:bb      #{'clojure.core_test.descendants/TestDescendantsRecord 'clojure.core_test.descendants/TestDescendantsType}
+                                 :default #{TestDescendantsRecord TestDescendantsType}) datatypes ::datatype
+                              #?(:bb      #{'clojure.core_test.descendants/TestDescendantsType}
+                                 :default #{TestDescendantsType}) datatypes ::mutable
+
+                              ; tag in both h and global hierarchy, only descendants in h are returned
+                              #{::a ::b ::c ::d} diamond ::root
+
+                              ; tag not in h but in global hierarchy
+                              nil datatypes ::root
+                              nil datatypes ::p-1
+                              nil datatypes ::p-2
+
+                              ; tag neither in h nor in global hierarchy
+                              nil datatypes ::d
+                              nil datatypes ::b
+                              nil datatypes ::a))
+
+      (testing "cannot get descendants by type inheritance, whether the tag is in h or not"
+        (are [h] #?(:cljs    (nil? (descendants h js/Object))
+                    :default (thrown? Exception (descendants h Object)))
+                 ; tag in h
+                 (derive (make-hierarchy) Object ::object)
+                 ; tag not in h
+                 diamond
+                 datatypes))
+
+      (testing "does not throw on invalid tag or hierarchy"
+        (are [invalid] (nil? (descendants invalid invalid))
+                       nil
+                       "anything"
+                       42
+                       3.14
+                       true
+                       false
+                       []
+                       {}
+                       #{}
+                       '())))))