I just found these Energizer self-test batteries in an old flashlight. : r/nostalgia
Great AA Alkaline Battery Test – Pt 3: The Results | Gough's Tech Zone
Amazon.com: D-FantiX Battery Tester, Universal Battery Checker Small Battery Testers for AAA AA C D 9V 1.5V Button Cell Household Batteries Model BT-168 : Electronics