The problem with "modern tests" is that they do NOT CHECK for high voltage leakage which is a huge problem with old condensers/ capacitors and sometimes with low quality "modern" replacements. The only "simple" (but not cheap) way I know of is to obtain an "old school" cap checker which HAS a LEAKAGE test. This type of test actually applies high voltage to the cap and checks leakage under those conditions. I toss most outboard caps not because of the value (capacitance) --which is MEANINGLESS if they have leakage---but rather because they are in fact "leaky"
I have a pair of old Eico testers which I'm hoping to "refurbish" as well as an older model Heathkit. The Heathkits especially, and especially the newer models--have gone absolutely nutcase on egag for price
My Heathkit is an older model like this photo I "stole" of the internet
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The Eico's are very similar in construction and operation to the Heath
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