Keep in mind that, depending on the amount of RAM you have installed, these tests will take some time to complete. But this isn't something you have to do regularly — perhaps once a year or even every few years, if you care to include it with regular system checks you perform on your Mac. (The only other regular one which I recommend is to check your hard drive for formatting errors.)
If any of the tests you run returns any status except for OK, then you should consider replacing it as soon as possible.
You can look up the type of RAM your system uses by choosing About This Mac from the Apple menu, where you should see the current RAM amount (8GB or 16GB, for example), its speed (1600MHz, say), and its type (DDR3 is one possibility). However, that's not all information you need; it's missing things like pin counts. You can find that specific information in Apple's support website, where it hosts an index of instructions for replacing RAM on your Mac.
If your Mac doesn't support user-upgradable memory (the Retina MacBook Pro, say, or the MacBook Air), then you'll need to contact an Apple technician.
Finally, if you do replace your Mac's RAM, be sure to keep the receipts, packaging, and other proofs of purchase for it. Most RAM manufacturers offer lifetime warranties for their products. So upon receiving your replacement, be sure to test it thoroughly, and then do so periodically to ensure it is working correctly. If not, you can then contact the manufacturer for a replacement or a market-value refund of the purchase price.
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