If the load on the three fuses is reasonably balanced, a millivolt-drop test might be done on the presently-installed fuses and fuseholders
See ecmweb.com/ar/electric_testing_contact_quality/index.htm—"Testing Contact Quality on Live Motor Starters". Understand that this involves dealing with energized circuits, so may not be appropriate unless you are adequately qualified and trained in live-troubleshooting practices.
Designers are sometimes pressured to make control gear as small a possible, and in doing so may choose class-CC over class-J fuses. I don’t think that’s always the best idea.