django-test-migrations Build status codecov Python Version PyPI - Django Version wemake-python-styleguide


Read the announcing post. See real-world usage example.


pip install django-test-migrations

We support several django versions:

Other versions might work too, but they are not officially supported.

Testing django migrations

Testing migrations is not a frequent thing in django land. But, sometimes it is totally required. When?

When we do complex schema or data changes and what to be sure that existing data won't be corrupted. We might also want to be sure that all migrations can be safely rolled back. And as a final touch we want to be sure that migrations are in the correct order and have correct dependencies.

Testing forward migrations

To test all migrations we have a Migrator class.

It has three methods to work with:

So, here's an example:

from django_test_migrations.migrator import Migrator

migrator = Migrator(database='default')

# Initial migration, currently our model has only a single string field:
# Note:
# We are testing migration `0002_someitem_is_clean`, so we are specifying
# the name of the previous migration (`0001_initial`) in the
# .apply_initial_migration() method in order to prepare a state of the database
# before applying the migration we are going to test.
old_state = migrator.apply_initial_migration(('main_app', '0001_initial'))
SomeItem = old_state.apps.get_model('main_app', 'SomeItem')

# Let's create a model with just a single field specified:
assert len(SomeItem._meta.get_fields()) == 2  # id + string_field

# Now this migration will add `is_clean` field to the model:
new_state = migrator.apply_tested_migration(
    ('main_app', '0002_someitem_is_clean'),
SomeItem = new_state.apps.get_model('main_app', 'SomeItem')

# We can now test how our migration worked, new field is there:
assert SomeItem.objects.filter(is_clean=True).count() == 0
assert len(SomeItem._meta.get_fields()) == 3  # id + string_field + is_clean

# Cleanup:

That was an example of a forward migration.

Backward migration

The thing is that you can also test backward migrations. Nothing really changes except migration names that you pass and your logic:

migrator = Migrator()

# Currently our model has two field, but we need a rollback:
old_state = migrator.apply_initial_migration(
    ('main_app', '0002_someitem_is_clean'),
SomeItem = old_state.apps.get_model('main_app', 'SomeItem')

# Create some data to illustrate your cases:
# ...

# Now this migration will drop `is_clean` field:
new_state = migrator.apply_tested_migration(('main_app', '0001_initial'))

# Assert the results:
# ...

# Cleanup:

Testing migrations ordering

Sometimes we also want to be sure that our migrations are in the correct order. And all our dependecies = [...] are correct.

To achieve that we have module.

That's how it can be used:

from django_test_migrations.plan import all_migrations, nodes_to_tuples

main_migrations = all_migrations('default', ['main_app', 'other_app'])
assert nodes_to_tuples(main_migrations) == [
    ('main_app', '0001_initial'),
    ('main_app', '0002_someitem_is_clean'),
    ('other_app', '0001_initial'),
    ('main_app', '0003_update_is_clean'),
    ('main_app', '0004_auto_20191119_2125'),
    ('other_app', '0002_auto_20191120_2230'),

This way you can be sure that migrations and apps that depend on each other will be executed in the correct order.

Test framework integrations 🐍

We support several test frameworks as first-class citizens. That's a testing tool after all!

Note that the Django post_migrate signal's receiver list is cleared at the start of tests and restored afterwards. If you need to test your own post_migrate signals then attach/remove them during a test.


We ship django-test-migrations with a pytest plugin that provides two convinient fixtures:

That's how it can be used:

import pytest

def test_pytest_plugin_initial(migrator):
    """Ensures that the initial migration works."""
    old_state = migrator.apply_initial_migration(('main_app', None))

    with pytest.raises(LookupError):
        # Models does not yet exist:
        old_state.apps.get_model('main_app', 'SomeItem')

    new_state = migrator.apply_tested_migration(('main_app', '0001_initial'))
    # After the initial migration is done, we can use the model state:
    SomeItem = new_state.apps.get_model('main_app', 'SomeItem')
    assert SomeItem.objects.filter(string_field='').count() == 0


We also ship an integration with the built-in unittest framework.

Here's how it can be used:

from django_test_migrations.contrib.unittest_case import MigratorTestCase

class TestDirectMigration(MigratorTestCase):
    """This class is used to test direct migrations."""

    migrate_from = ('main_app', '0002_someitem_is_clean')
    migrate_to = ('main_app', '0003_update_is_clean')

    def prepare(self):
        """Prepare some data before the migration."""
        SomeItem = self.old_state.apps.get_model('main_app', 'SomeItem')
        SomeItem.objects.create(string_field='a b')

    def test_migration_main0003(self):
        """Run the test itself."""
        SomeItem = self.new_state.apps.get_model('main_app', 'SomeItem')

        assert SomeItem.objects.count() == 2
        assert SomeItem.objects.filter(is_clean=True).count() == 1

Testing migration names

django generates migration names for you when you run makemigrations. And these names are bad (read more about why it is bad)! Just look at this:

What does this migration do? What changes does it have?

One can also pass --name attribute when creating migrations, but it is easy to forget.

We offer an automated solution: django check that produces a warning for each badly named migration.

Add our check into your INSTALLED_APPS:

    # ...

    # Our custom check:

And then in your CI run:

python check --deploy --fail-level WARNING

This way you will be safe from wrong names in your migrations.

Do you have a migrations that cannot be renamed? Add them to the ignore list:


    ('main_app', '0004_auto_20191119_2125'),
    ('dependency_app', '0001_auto_20201110_2100'),

And we won't complain about them.

Or you can completely ignore entire app:


    ('dependency_app', '*'),
    ('another_dependency_app', '*'),


This project is based on work of other awesome people: