diff --git a/installed-tests/js/testSystem.js b/installed-tests/js/testSystem.js
index 927c715..5897632 100644
--- a/installed-tests/js/testSystem.js
+++ b/installed-tests/js/testSystem.js
@@ -1,4 +1,5 @@
 const System = imports.system;
+const GObject = imports.gi.GObject;
 
 describe('System.addressOf()', function () {
     it('gives the same result for the same object', function () {
@@ -13,6 +14,25 @@ describe('System.addressOf()', function () {
 
 describe('System.version', function () {
     it('gives a plausible number', function () {
-        expect(System.version).not.toBeLessThan(13600);
+        expect(System.version).not.toBeLessThan(14700);
+    });
+});
+
+describe('System.refcount()', function () {
+    it('gives the correct number', function () {
+        let o = new GObject.Object({});
+        expect(System.refcount(o)).toEqual(1);
+    });
+});
+
+describe('System.gc()', function () {
+    it('works properly', function () {
+        expect(System.gc()).not.toBeDefined();
+    });
+});
+
+describe('System.clearDateCaches()', function () {
+    it('works properly', function () {
+        expect(System.clearDateCaches()).not.toBeDefined();
     });
 });
