What resistance/ load do battery testers (AA or AAA) use in Ohms please
I've used a 10 Ohm 5 Watt resistor in the past and it works well for testing both Zinc-Carbon and Alkaline cells - both "AA" and "AAA".

You will have a current up to 160 mA which is enough to load the cell and show its true voltage at that current level.

A new cell will have a voltage exceeding 1.5 Vdc (often above 1.6 Vdc); a used but still usable cell will have a voltage between 1.2 to 1.5 Vdc; a weak cell will have a voltage between 1.0 to 1.2 Vdc.

A cell with a loaded voltage less than 1.0 Vdc is considered to be dead.  Some stuff might run from it but not for long.