utils.testhelpers — Testing utilities¶

Testing Django migrations¶

Warning

You can not test migrations if you have a MIGRATION_MODULES setting that disabled migrations. So make sure you remove that setting if you have it in your test settings.

Guide¶

Lets say you have the following model:

class Node(models.Model):
    name = models.CharField(max_length=255)

You have an initial migration, and you have created a migration named 0002_suffix_name_with_stuff which looks like this:

suffix = ' STUFF'

def add_stuff_to_all_node_names(apps, schema_editor):
    Node = apps.get_model('myapp', 'Node')
    for node in Node.objects.all():
        node.name = '{}{}'.format(node.name, suffix)
        node.save()

def reverse_add_stuff_to_all_node_names(apps, schema_editor):
    Node = apps.get_model('myapp', 'Node')
    for node in Node.objects.all():
        if node.name.endswith(suffix):
            node.name = node.name[:-len(suffix)]
            node.save()

class Migration(migrations.Migration):
    dependencies = [
        ('myapp', '0001_initial'),
    ]

    operations = [
        migrations.RunPython(add_stuff_to_all_node_names, reverse_code=reverse_add_stuff_to_all_node_names),
    ]

Note

You can not test migrations that can not be reversed, so you MUST write reversible migrations if you want to be able to test them. Think of this as a good thing - it forces you to write reversible migrations.

To test this, you can write a test case like this:

from ievv_opensource.utils.testhelpers import testmigrations

class TestSomeMigrations(testmigrations.MigrationTestCase):
    app_label = 'myapp'
    migrate_from = '0001_initial'
    migrate_to = '0002_suffix_name_with_stuff'

    def test_migrate_works(self):

        # Add some data to the model using the ``apps_before`` model state
        Node = self.apps_before.get_model('myapp', 'Node')
        node1_id = Node.objects.create(
            name='Node1'
        ).id
        node2_id = Node.objects.create(
            name='Node2'
        ).id

        # Migrate (run the 0002_suffix_name_with_stuff migration)
        self.migrate()

        # Test using the ``apps_after`` model state.
        Node = self.apps_after.get_model('myapp', 'Node')
        self.assertEqual(Node.objects.get(id=node1_id).name, 'Node1 STUFF')
        self.assertEqual(Node.objects.get(id=node2_id).name, 'Node2 STUFF')

    def test_reverse_migrate_works(self):

        # First, we migrate to get to a state where we can reverse the migration
        self.migrate()

        # Add some data to the model using the ``apps_after`` model state
        Node = self.apps_after.get_model('myapp', 'Node')
        node1_id = Node.objects.create(
            name='Node1 STUFF'
        ).id
        node2_id = Node.objects.create(
            name='Node2 STUFF'
        ).id

        # Reverse the migration
        self.reverse_migrate()

        # Test using the ``apps_before`` model state.
        Node = self.apps_before.get_model('myapp', 'Node')
        self.assertEqual(Node.objects.get(id=node1_id).name, 'Node1')
        self.assertEqual(Node.objects.get(id=node2_id).name, 'Node2')

utils.testhelpers — Testing utilities¶

Testing Django migrations¶

Guide¶

The MigrationTestCase class¶