I got the itch to get a water test kit recently after doing with a DIY sump that I keep adding more and more media to as I found extra available. The only definitive way to tell if I really had more than enough media was to test parameters.
The last time I'd ever bothered with testing was all the way back in my early high school years when I setup my first african cichlid tank. Since then I've never really felt the need to test again (until now). Once you get a good handle on the ideas behind keeping cichlids - good water source, overfiltering tanks, and sufficient water changes. If something goes astray, the water clarity and fish will let you know.
Anyways, I finally got around to testing my big tank today while doing a water change. Before anyone's concerned, the testing was performed while watching it drain; not while filling it up.

API master test kit; dates on test solutions were good through 2019.
Nitrite - I skipped the ammonia testing, as the tank has been running since November, so if there was any ammonia, there was also very likely to be nitrite.
Results: 0ppm (accuracy was within 1/4ppm)
Thoughts: As expected
pH - I realized almost immediately this was a worthless test, as there was a specific "High pH" test bottle as well.
Results: Off the chart
Thoughts: LOL
High pH - My recollection from many, many years ago when I last had my water source tested was that the LFS said it was above 7.8, but didn't want to give me a specific number and said it was definitely sufficient for african cichlids. This test kit had better accuracy.
Results: 8.2 (accuracy within 0.2)
Thoughts: I'm not surprised and pleased with the results.
Nitrate - This is the one I was really interested in the most. I'm doing somewhere right around weekly water changes of ~17-20%. There's a lot of fish in the tank and I feel like I'm feeding a pond of bluegills tossing in food 1-2 times per day. I keep reading different target values for what is sufficient vs what is good vs what is best, etc, and wasn't sure where this was really going to end up.
Results: 0ppm (accuracy within 5ppm)
Thoughts: The color wasn't anywhere close to anything other than 0, but I really expected this would have had a measurable value. I do have some good bio going, but didn't think I'd have sufficient amount of anaerobic bacteria to consume sufficient amounts of nitrate.
Could I have goofed the nitrate testing up? It seemed pretty fool proof to mix X drops of solution #1 and then X drops of solution #2, mix, and watch the resulting color. I even let it sit for another 5 minutes or so and the color was stable. On the bright side, it didn't register some ridiculously high number I suppose.