Why Capacitors go bad

I have a fluke 87 which has a capacitor test on it but I haven't figured it out.
To my knowledge none of the modern solid state testers have a leakage test. I have a couple of "china" testers which can VERY accurately give you the capacitance value down to very small values, and therefore quite useful. But for automotive caps leakage testers are far and few

The "Bruno" tester I use has one, as do the old "Merc-o-Tronic" testers of which I have two "non working" ones

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