The most important aspect of pool-light safety is the GFCI. Testing regularly (monthly is recommended) is what tells you if you are protected. Most good GFCI devices and breakers will come with a small chart that allows for keeping a record. Unfortunately this is seldom done, even on commercial pools where some jurisdictions require it to be done daily along with the water-chemistry testing.
Another problem with most pools is that GFCI devices do have a "shelf life."
This, from Homepreservationmanual.com:
"The average GFCI outlet has a service life of only 10 years. If your home is older than that, there’s a good chance that at least some of your GFCI outlets aren’t working properly. If your area is subject to corrosion, high humidity and/or frequent storms or power surges, it is possible for GFCI outlets to become non-functional in 5 years or even less."
GFCI devices in most pool environments certainly fit the conditions listed as limiting the life to 5 years. When I first got into this business, every electrical class, seminar, etc. that I took encouraged replacement every 5 years. Since "safety doesn't sell," it is almost impossible to get customers to do this unless the device tests as bad. The problem with that thinking is the "test" may be when a light has an issue and the device fails. If nothing else, a good practice is to replace the device each time a bulb is replaced and always if the whole fixture is replaced.
Pool water is highly conductive. Mixing that with electricity and your family never works out well. Best practice; test regularly. If it is over 5-years-old, replace it, they don't cost that much. Get a name-brand device, not the cheapest on E-Bay. Don't be afraid of your pool, just make it safe.
