BASE_DATE = timezone.datetime(2022, 7, 20, 20)
        test_dag_id = "test_get_task_instances_before"
        test_task_id = "the_task"
        test_dag = DAG(dag_id=test_dag_id, start_date=BASE_DATE)
        EmptyOperator(task_id=test_task_id, dag=test_dag)
        session = settings.Session()
        def dag_run_before(delta_h=0, type=DagRunType.SCHEDULED):
            dagrun = test_dag.create_dagrun(
                state=State.SUCCESS, run_type=type, run_id=f"test_{delta_h}", session=session
            )
            dagrun.start_date = BASE_DATE + timedelta(hours=delta_h)
            dagrun.execution_date = BASE_DATE + timedelta(hours=delta_h)
            return dagrun
        dr1 = dag_run_before(delta_h=-1, type=DagRunType.MANUAL)  
        dr2 = dag_run_before(delta_h=-2, type=DagRunType.MANUAL)  
        dr3 = dag_run_before(delta_h=-3, type=DagRunType.MANUAL)  
        dr4 = dag_run_before(delta_h=-4, type=DagRunType.MANUAL)  
        dr5 = dag_run_before(delta_h=-5)  
        dr6 = dag_run_before(delta_h=-6)  
        dr7 = dag_run_before(delta_h=-7)  
        dr8 = dag_run_before(delta_h=-8)  
        session.commit()
        REF_DATE = BASE_DATE
        assert set([dr.run_id for dr in [dr1]]) == set(
            [
                ti.run_id
                for ti in test_dag.get_task_instances_before(base_date=REF_DATE, num=1, session=session)
            ]