test_migrations.py

import pytest
from alembic.migration import MigrationContext
from sqlalchemy import create_engine


@pytest.mark.noautofixt()
def test_migrations_no_branches(db_uri):
    engine = create_engine(db_uri)
    conn = engine.connect()
    context = MigrationContext.configure(conn)

    assert len(context.get_current_heads()) == 1, (
        "\n\n!!!\n\nDetected a branching of db migrations. This is caused by multiple `down_revision`s referring to the"
        " same migration.\n\nPlease resolve this by updating either one of these migrations: "
        f"{context.get_current_heads()}.\n\n!!!\n\n"
    )