def test_with_good_ids():
    class Migration_A(object):
        migration_id = "A"

    class Migration_B(object):
        migration_id = "B"


    validate_all_migrations_have_ids([Migration_A, Migration_B])
def test_with_migrations_with_falsy_ids(migration_class):
    with pytest.raises(ValueError):
        validate_all_migrations_have_ids([migration_class])