Bare in mind that proper testing will likely require soldering wires onto the pads (4 wires, two for sense), otherwise it's pretty fiddly.
I thought about using thin metal stripes: two between the battery plus terminal and the Betteriser, with isolation between, so that I can measure the current into the Batteriser and the battery voltage. For the output voltage and current I can just plug it in a battery holder and solder wires to the battery holder. But right, might be fiddly this way and the stripes might not make contact to the pads. I'm not good with mechanics anyway, so soldering wires to the Batterieser would be easier. If it is normal PCB (maybe even gold plated), would be no problem. Soldering to the negative terminal could be a problem, stainless steel doesn't like this, but some windings of bare wire and pressing it against the contact with a paper clip and electrical tape should do it for this side.
Don't know if it is necessary to use 4 wires, I was planning to do some tests with 100 mA and 10 mA, but might be a good idea to check the limits, too, because as we know, the webpage says it can handle all the current a battery can deliver
Problem with this is, Batteroo will say this is not a proper test, because the battery would provide a lot of cooling, and this might be less efficient with soldered wires between the battery positive terminal and the pad, if it creates a gap, but we'll see.
But might be good anyway to test it without a battery with a power supply. I just found out how to control my SPD3303D power supply over USB from a Python script from my Linux system (it uses the USBTMC protocol, which a lot of instruments and power supplies use, e.g. some Keysight gear, too). So I can create a lot of characteristics curves automatically with a script for different input voltages and loads, without having to wait until a battery discharges.
A problem is that I have only one high quality 4 3/4 digits benchtop multimeter, which I can read over RS232. But I have an ADG608 8x1 mux in my parts bin, which I can power with +/-5V to prevent non-linear behaviour at low voltages, and I have a uCurrent Gold, which is perfect with the low burden voltage to measure the current into the Batteriser. Too bad I sold my old uCurrent, but the output current is no problem to measure with something like an 1 ohm and 0.1 ohm shunt. I guess the ADG608 has no problems switching millivolts?