              e.name for e in Experiment.objects.filter(estimated_time__lt=F('end') - F('start'))
          ]
          self.assertEqual(over_estimate, ['e4'])
  
      def test_duration_with_datetime(self):
          # Exclude e1 which has very high precision so we can test this on all
          # backends regardless of whether or not it supports
          # microsecond_precision.
 
</s> remove         # Discard any fractional microseconds due to floating point arithmetic.
        return round(value.total_seconds() * 1000000)
 </s> add         return duration_microseconds(value) </s> remove     return (left - right).total_seconds() * 1000000
 </s> add     return duration_microseconds(left - right)
    @skipUnlessDBFeature('supports_temporal_subtraction')
    def test_datetime_subtraction_microseconds(self):
        delta = datetime.timedelta(microseconds=8999999999999999)
        Experiment.objects.update(end=F('start') + delta)
        qs = Experiment.objects.annotate(
            delta=ExpressionWrapper(F('end') - F('start'), output_field=models.DurationField())
        )
        for e in qs:
            self.assertEqual(e.delta, delta)

              e.name for e in Experiment.objects.filter(estimated_time__lt=F('end') - F('start'))
          ]
          self.assertEqual(over_estimate, ['e4'])
  
    @skipUnlessDBFeature('supports_temporal_subtraction')
    def test_datetime_subtraction_microseconds(self):
        delta = datetime.timedelta(microseconds=8999999999999999)
        Experiment.objects.update(end=F('start') + delta)
        qs = Experiment.objects.annotate(
            delta=ExpressionWrapper(F('end') - F('start'), output_field=models.DurationField())
        )
        for e in qs:
            self.assertEqual(e.delta, delta)

      def test_duration_with_datetime(self):
          # Exclude e1 which has very high precision so we can test this on all
          # backends regardless of whether or not it supports
          # microsecond_precision.
keep keep keep add keep keep keep keep
 Fixed #28926 -- Fixed loss of precision of big DurationField values on SQLite and MySQL. 
tests/expressions/tests.py