test_stairway.py

"""
Test can find forgotten downgrade methods, undeleted data types in downgrade
methods, typos and many other errors.

Does not require any maintenance - you just add it once to check 80% of typos
and mistakes in migrations forever.
"""
import pytest
from alembic.command import downgrade, upgrade
from alembic.config import Config
from alembic.script import Script, ScriptDirectory

from staff.utils import alembic_config_from_url


def get_revisions():
    # Create Alembic configuration object
    # (we don't need database for getting revisions list)
    config = alembic_config_from_url()

    # Get directory object with Alembic migrations
    revisions_dir = ScriptDirectory.from_config(config)

    # Get & sort migrations, from first to last
    revisions = list(revisions_dir.walk_revisions('base', 'heads'))
    revisions.reverse()
    return revisions


@pytest.mark.parametrize('revision', get_revisions())
def test_migrations_stairway(alembic_config: Config, revision: Script):
    upgrade(alembic_config, revision.revision)

    # We need -1 for downgrading first migration (its down_revision is None)
    downgrade(alembic_config, revision.down_revision or '-1')
    upgrade(alembic_config, revision.revision)