Currently, the test suite is using the code in https://github.com/ramses-organisation/ramses/blob/stable/tests/visu/visu_ramses.py to read the simulation outputs.

It is a cheap copy of the python reader in the osyris package.

It could be easier to just install osyris and use it to visualize the test results?
It would make the code in e.g. https://github.com/ramses-organisation/ramses/blob/stable/tests/hydro/implosion/plot-implosion.py much simpler.
It would also remove the need for maintaining the code in visu_ramses.py.

This would however mean that if a new version of osyris is released with breaking changes, this could break the test suite.
It would be a good idead to pin the version of osyris that is being installed for the tests, to make sure that we only update osyris on purpose, and not silently in the background.