I bought a tube tester when I started playing with DHT and rectifiers. Having one actually saved my new amp from a shorted rectifier. It was a NOS 5r4gy from 1956 that I bought as a group of 4. They were time capsule condition yet one was bad
Your best bet is to pay a few bucks extra to have pairs and quads matched. Also a good idea to have dual triodes matched and screened for noise. My best quality tube sets have been purchased from trusted sources that match. This was proven after testing a bunch of tubes collected over the years
When I receive them I also test them.
I was lucky, I bought a mint Hickok that works great and is accurate with several "bogey" tubes so it's more than accurate for weeding out bad tubes and matching good ones. MOST TUBE TESTERS NEED WORK. Always remember that if thinking of getting one.
Almost all of my gear has tubes so for me it is peace of mind.
It is rare to find one this nice that works so use caution if looking for one. Best to just buy from vendors with an Amplitrex or similar computerized test equipment.