We have flaky scheduler test:


https://github.com/apache/airflow/pull/11659/checks?check_run_id=1279791496#step:6:527


_______________ TestSchedulerJob.test_scheduler_task_start_date ________________

self = <tests.jobs.test_scheduler_job.TestSchedulerJob testMethod=test_scheduler_task_start_date>

    def test_scheduler_task_start_date(self):
        """
        Test that the scheduler respects task start dates that are different from DAG start dates
        """
    
        dagbag = DagBag(dag_folder=os.path.join(settings.DAGS_FOLDER, "no_dags.py"), include_examples=False)
        dag_id = 'test_task_start_date_scheduling'
        dag = self.dagbag.get_dag(dag_id)
        dag.is_paused_upon_creation = False
        dagbag.bag_dag(dag=dag, root_dag=dag)
    
        # Deactivate other dags in this file so the scheduler doesn't waste time processing them
        other_dag = self.dagbag.get_dag('test_start_date_scheduling')
        other_dag.is_paused_upon_creation = True
        dagbag.bag_dag(dag=other_dag, root_dag=other_dag)
    
        dagbag.sync_to_db()
    
        scheduler = SchedulerJob(executor=self.null_exec,
                                 subdir=dag.fileloc,
                                 num_runs=2)
        scheduler.run()
    
        session = settings.Session()
        tiq = session.query(TaskInstance).filter(TaskInstance.dag_id == dag_id)
        ti1s = tiq.filter(TaskInstance.task_id == 'dummy1').all()
        ti2s = tiq.filter(TaskInstance.task_id == 'dummy2').all()
        self.assertEqual(len(ti1s), 0)
>       self.assertEqual(len(ti2s), 2)
E       AssertionError: 1 != 2
tests/models/test_taskinstance.py
dag.create_dagrun(
                run_type=DagRunType.SCHEDULED,
                state=state,
                execution_date=execution_date,
                start_date=pendulum.now('UTC'),
                session=session,
            )
            ti = TI(task=task, execution_date=execution_date)
            ti.set_state(state=State.SUCCESS, session=session)
            return ti
        with create_session() as session:  
            date = cast(pendulum.DateTime, pendulum.parse('2019-01-01T00:00:00+00:00'))
            ret = []
            for idx, state in enumerate(scenario):
                new_date = date.add(days=idx)
                ti = get_test_ti(session, new_date, state)
                ret.append(ti)
            return ret
    _prev_dates_param_list = (
        param('cron/catchup', '0 0 * * * ', True),
        param('cron/no-catchup', '0 0 * * *', False),
        param('no-sched/catchup', None, True),
        param('no-sched/no-catchup', None, False),
        param('timedelta/catchup', datetime.timedelta(days=1), True),
        param('timedelta/no-catchup', datetime.timedelta(days=1), False),
    )
    @parameterized.expand(_prev_dates_param_list)
    def test_previous_ti(self, _, schedule_interval, catchup) -> None: