If I'm the Paul you're referring to, it would be better to CC me in the
future, as I'm not subscribed to the list and only intermittently check
it (which happens more often when I'm submitting patches).
Actually, I'm not the original author of the fenics package; I just
added support for #:tests? (and fixed the sanity check), so I don't know
why the tests are run with mpirun.
However, the reason I had added support for the #:tests?
flag is to skip the fenics tests, which were failing for me.
I'm no expert in MPI and pytest, but it does seem that pytest_mpi [1] is
recommended when combining the two, and there are no instances of
@pytest.mark.mpi in the fenics repository.
Further, running pytest tests under MPI is accomplished with [2]:
mpirun -n 2 python -m pytest --with-mpi
In other words, it seems as if the current tests are repeated in
parallel, as Ontje discovered.
The patch looks good to me.