If you can get your hands on a lab psu that can output 20a, that’s the ticket. Set the voltage low for safety, like 2v should be okay. Voltage does not affect heat and fusing. Set current limit close to zero, short across the strip, slowly turn up the current until you see what you want. Most reasonably priced lab PSUs stop at 10a. You might be able use half thickness fuse to test. Not sure if things are linear enough with heat affecting things.
There’s also Ruideng DPS-5020 which might be cheaper and more compact if you can feed it enough power.
Alternatively you can also try one of these
There are many variants with different prices. The limit for the linked one is 150w or 20a whichever is reached first. If you set voltage under 7.5v you can pull 20a. Might need to watch the cooling.
IIRC the one I linked (purple fan with pretty displa) is analog controls. The display shows what’s happening, and you twiddle the knobs to change parameters. No digital control.
The one below has an ugly display and is only 10A, but has digital control (you set the parameters you want numerically, then hit the “on” button).
Maybe 2 of those in parallel to get 20a of load…
All that said, I think you should skip the cell level fusing.