One of the good things about MC4X60V50A (or steampunk controller if you like) is that MCU is powered separately from the MOSFET driver part. This enables me to use a USB, power the MCU and write test code without worrying about the 3KW driver part.
For actual testing I can settle with smaller motors to test logic. I have plenty of Nema17 rated to ca 2A, one 3-Phase rated 30A, another rated 15A and I have even ordered one rated 90A max. The challenge is more that I at present only can support max 30A from Lab PSU’s. But, that will have to do for now.