Hardware vs. Wetware
When you hear RAM memory test, you might think of diagnostic software like MemTest86 that checks your computer's sticks of RAM for errors. However, a human memory test checks your 'wetware' - your brain.
Storage vs. Processing
Computer RAM is temporary storage for fast access. Human working memory functions similarly. It holds information you are currently using. Just like a computer slows down if its RAM is full, your brain struggles if you try to hold too much in your working memory.
Upgradability
You can easily buy more sticks to pass a computer RAM memory test. For your brain, you can't install new hardware, but you can different software - meaning, you can learn better memorization techniques to improve your capacity.