) -> DagRun:
    """Create a DAG run, replacing an existing instance if needed to prevent collisions.
    This function is only meant to be used by :meth:`DAG.test` as a helper function.
    :param dag: DAG to be used to find run.
    :param conf: Configuration to pass to newly created run.
    :param start_date: Start date of new run.
    :param execution_date: Logical date for finding an existing run.
    :param run_id: Run ID for the new DAG run.
    :return: The newly created DAG run.
    """
    log.info("dagrun id: %s", dag.dag_id)
    dr: DagRun = (
        session.query(DagRun)
        .filter(DagRun.dag_id == dag.dag_id, DagRun.execution_date == execution_date)
        .first()
    )
    if dr:
        session.delete(dr)
        session.commit()
    dr = dag.create_dagrun(
        state=DagRunState.RUNNING,
        execution_date=execution_date,
        run_id=run_id,
        start_date=start_date or execution_date,
        session=session,
        conf=conf,
    )
    log.info("created dagrun %s", dr)
    return dr