You are thinking the right thing, but focusing on the wrong conclusion.
Do not focus on success but on failure:
start_service.py &
# wait until service is ready then run:
parallel --halt now,fail=1 -j0 ::: test1.py test2.py
# stop service
stop_service.py
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…