Refs #2443 -- Allowed creation of objects with NULL DurationFields

    def get_db_prep_value(self, value, connection, prepared=False):

        if connection.features.has_native_duration_field:

            return value

        if value is None:

            return None

        return value.total_seconds() * 1000000

    def get_db_converters(self, connection):

    field = models.DurationField()

class NullDurationModel(models.Model):

    field = models.DurationField(null=True)

class PrimaryKeyCharModel(models.Model):

    string = models.CharField(max_length=10, primary_key=True)

from django.db import models

from django.test import TestCase

from .models import DurationModel

from .models import DurationModel, NullDurationModel

class TestSaveLoad(TestCase):

        loaded = DurationModel.objects.get()

        self.assertEqual(loaded.field, duration)

    def test_create_empty(self):

        NullDurationModel.objects.create()

        loaded = NullDurationModel.objects.get()

        self.assertEqual(loaded.field, None)

class TestQuerying(TestCase):