how are you testing your own tubes?

Testers  are hard to find in good shape and they they need to be calibrated to get the most accurate reading so best to get them checked at a shop. I'm thinking yearly for power tubes and every few years for low power tubes like preamp tubes and drivers. Eventually they will fail but you will most likely tell much before that by poor sound quality, well unless they fail spectacularly like internal shorting.

of course most of us i'd imagine just wait until they sound bad, microphonic or fail and replace.

+1 glennewdick

If you are just dipping your toe into the water, you will probably do fine just winging it.  If your amp has a standby switch for the power tubes, it's best to employ that to run new tubes in for a while before putting the amp in operate mode.  That said, such products are not the majority.  Also certain products do better with a bad tube than others.  Personally, I don't really know why more amps don't fail gracefully when dealing with a bad tube.  But again, lets presume happy path, you'll likely do fine.

You may want to sniff around your local area to find out if you actually can get someone to test your tubes.  Audio groups, guitar amplifier techs / guitar shops, and even putting an ad on Craigslist will likely turn something up so long as you're reasonably close to civilization.

At some point, if you find yourself deep enough into tubes, you will push yourself into buying a tube tester.  By that I mean, you'll be buying and trying tubes on a level that justifies the investment more than not having it.  It's not as painful as it sounds.  There are a few new production items that offer decent performance and cost, check the guitar focused solutions.  Really, in this age, it makes too much sense to offer a software based solution that employs minimal and relatively low cost hardware all at a very attainable price.  I think those do exist on some level whenever I look into it, but I feel they should be far more ubiquitous 

I've had very good luck with reputable dealers like thetubestore.com, Upscale, and Tube Depot, who seemingly test things before shipping, and Ebay sellers with lots of positive feedback and a return policy for NOS tubes. Only one tube has committed "tubiscide" and that was something I observed when a NOS Phillips military spec 12AT7 flamed out...tubestore warranty to the rescue...

Buy them from Vintage Tube Services or Brent Jesse and you will not have to test them as it will be done already.Good luck!!

Ask some old timers in your neighborhood. I got a hickok 600a from my neighbor, in perfect shape, for 50$. He was so happy I was into tubes. He also gave me a huge box of tubes. Also, check on eBay. There’s plent o tube testers for sale. Good luck!

I think knowing what you are testing helps determine correlative measurements that could determine performances.  Tubes tested from various houses are provided with multiple measurement data.  With that in mind, use the right measurements per application.  Tube testers - If you are testing tubes and want reliability with your readings than modern equipment is available.  I use MaxiMatcher II.  http://maximatcher.com/maximatcher.htmlFinding a good or better tube tester of the antique version is sometimes difficult.  I learned from multiple purchases.  My choice unit is a B & K Dyna-Jet in almost pristine condition.  
Good Luck.