At some point, we should update the jointcal testdata to reflect the latest processCcd output (e.g. using the new Pessimistic matcher) processed with a more modern reference catalog (likely PS1 for photometry, Gaia for astrometry). This should allow us to un-skip several of the existing tests (e.g. DeCAM photometry tests) that are currently skipped because of bad test data, and remove old-style sourceSelector flags, etc. This would also be the time to update testdata_jointcal to the gen3 butler format.
As part of this work, we should investigate in detail the various chi2/ndof values computed by the tests (these were changed as part of DM-17595, without in-depth study). This would be the time to really test assumptions about e.g. no_rank_update or line search astrometry tests not changing the default chi2, when a highly accurate reference catalog is used (Gaia).
I would expect this work to be delayed for a year or so, until all of the above pieces are nicely settled into place.