Fixed #28926 -- Fixed loss of precision of big DurationField values on SQLite and MySQL.

tests/utils_tests/test_duration.py

@@ -2,7 +2,9 @@ import datetime
 import unittest
 
 from django.utils.dateparse import parse_duration
-from django.utils.duration import duration_iso_string, duration_string
+from django.utils.duration import (
+    duration_iso_string, duration_microseconds, duration_string,
+)
 
 
 class TestDurationString(unittest.TestCase):
@@ -79,3 +81,17 @@ class TestParseISODurationRoundtrip(unittest.TestCase):
     def test_negative(self):
         duration = datetime.timedelta(days=-1, hours=1, minutes=3, seconds=5)
         self.assertEqual(parse_duration(duration_iso_string(duration)).total_seconds(), duration.total_seconds())
+
+
+class TestDurationMicroseconds(unittest.TestCase):
+    def test(self):
+        deltas = [
+            datetime.timedelta.max,
+            datetime.timedelta.min,
+            datetime.timedelta.resolution,
+            -datetime.timedelta.resolution,
+            datetime.timedelta(microseconds=8999999999999999),
+        ]
+        for delta in deltas:
+            with self.subTest(delta=delta):
+                self.assertEqual(datetime.timedelta(microseconds=duration_microseconds(delta)), delta)