Issue #13846: Add time.monotonic(), monotonic clock.
diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py
index f299266..a89c511 100644
--- a/Lib/test/test_time.py
+++ b/Lib/test/test_time.py
@@ -331,16 +331,32 @@
             pass
         self.assertEqual(time.strftime('%Z', tt), tzname)
 
+    @unittest.skipUnless(hasattr(time, 'monotonic'),
+                         'need time.monotonic()')
+    def test_monotonic(self):
+        t1 = time.monotonic()
+        t2 = time.monotonic()
+        self.assertGreaterEqual(t2, t1)
+
+        t1 = time.monotonic()
+        time.sleep(0.1)
+        t2 = time.monotonic()
+        dt = t2 - t1
+        self.assertGreater(t2, t1)
+        self.assertAlmostEqual(dt, 0.1, delta=0.2)
+
     def test_wallclock(self):
         t1 = time.wallclock()
         t2 = time.wallclock()
+        # may fail if the system clock was changed
         self.assertGreaterEqual(t2, t1)
 
         t1 = time.wallclock()
         time.sleep(0.1)
         t2 = time.wallclock()
-        self.assertGreater(t2, t1)
         dt = t2 - t1
+        # may fail if the system clock was changed
+        self.assertGreater(t2, t1)
         self.assertAlmostEqual(dt, 0.1, delta=0.2)
 
     def test_localtime_failure(self):