Parallel Execution and File Comparison

About

I am currently writing unit tests for a module in the dune-pdelab repository, under the supervision of @linus.seelinger. We make use of dune-testtools for several tests and its capabilities are really impressive.

At one point in the tests, we execute a simulation in parallel and would like to compare the resulting vtu files to corresponding reference files. The way I solved this problem is to essentially combine the existing 'dune_execute_parallel.py' and 'dune_vtkcompare.py' scripts into a new script 'dune_vtkcompare_parallel.py' and add it to the dune-testtools module. This works fine locally, however as we want to use it in dune-pdelab, this would require also adding this script to this repository.

I am new to GitLab, so please excuse me if a Merge Request is not the right format for addressing such a problem. To recapitulate, the following are my issues:

• Is this the right way to do it ? Is there an alternative to it, which does not require changes in dune-testtools ?
• If it is the right way, is there criticism regarding the code ?

State of the Branch

As mentioned above, I combined the 'dune_execute_parallel.py' and 'dune_vtkcompare.py' scripts and added some documentation. The wrapper works as intended for the test where we needed it.

The pipeline fails at the moment, however the only test failing is the PEP8 compliance as far as I can see. In my local repository this is also the case for the master branch.