Resource leak in tests

[iasoon]

When running the test suite, the following message appears:

2022-08-12 20:12:41,753	WARNING worker.py:1404 -- WARNING: 46 PYTHON worker processes have been started on node: 711ff7ca6e04ebd43f741dc793cac210f317e2cb1a237efd6ed17789 with address: 10.1.0.30. This could be a result of using a large number of actors, or due to tasks blocked in ray.get() calls (see https://github.com/ray-project/ray/issues/3644 for some discussion of workarounds).

As the number of worker processes keeps increasing as the test suite progresses, it looks like we have a resource leak somewhere in our code.

[pabloem]

hmmm thanks for finding that. I'll try to debug this week...

[pabloem]

This should clean up all Ray resouces after every test:
#40

Note there's the IMPULSE element that we were creating in a 'global' context.

[pdames]

@iasoon @pabloem Do we still have known issues with resource leaks during test runs? Does this need further investigation or is it ready to be closed?