No, charging isn’t in question. They charge fine.

Get something like this:
https://www.ebay.com/itm/DC-12V-Battery-Capacity-Tester-Battery-Life-Internal-Resistance-Analyzer/263358206343

And a battery holder like this:
https://www.ebay.com/itm/Plastic-Battery-Holder-Storage-Box-Case-for-1x-2x-3x-4x-18650-Batteries-Wire/332855641026

These work quite well, and you can test capacity very accurately, along with internal resistance.