TrackrefTestCase.test_get_oldest: protect from lack of precision

tests/test_utils_trackref.py

@@ -1,7 +1,10 @@
 import unittest
 from io import StringIO
+from time import sleep, time
 from unittest import mock
 
+from twisted.trial.unittest import SkipTest
+
 from scrapy.utils import trackref
 
 
@@ -55,7 +58,18 @@ Foo                                 1   oldest: 0s ago\n\n''')
 
     def test_get_oldest(self):
         o1 = Foo()  # NOQA
+
+        o1_time = time()
+
         o2 = Bar()  # NOQA
+
+        o3_time = time()
+        if o3_time <= o1_time:
+            sleep(0.01)
+            o3_time = time()
+        if o3_time <= o1_time:
+            raise SkipTest('time.time is not precise enough')
+
         o3 = Foo()  # NOQA
         self.assertIs(trackref.get_oldest('Foo'), o1)
         self.assertIs(trackref.get_oldest('Bar'), o2)