I've replicated the issue stu saw by adding a deliberate source of nondeterminstic failure to a pants test, namely adding

from random import randint; assert 0 = randint(1, 2000)

so that the test will always fail but in a different way each time. I can see that every time I change the exact number in the randint line, I see one additional instance of the MultiPlatformProcess corresponding to the pytest runner execute

i.e. I see

[INFO] Completed: - Run Pytest for src/python/pants/build_graph/address_test.py:tests

in an effort to debug this I added a debug print

log::warn!("Calling complete(), node: {:?}", entry.node());

to the

complete()

method in

graph/src/lib.rs