Fix ParticleFile test cases #2185
Description
Some of the test_particlefile.py test cases currently are disabled (xfailed/skipped) or exist as stubs. This issue is to track progress on re-enabling these important test cases.
Blocked by #2180
This is a very important test; we really shouldn't forget about this. Will you do it in a next PR?
Originally posted by @erikvansebille in #2142 (comment)