On the new Gauntlet Podcast we talk with designers Rae Nedjadi @temporalhiccup and David Miessler-Kubanek @AquaVertigo about their experiences with playtesting tabletop rpgs.
Find that here: https://gauntlet-rpg.com/blog/playtesting-ttrpgs-insights-discussion
The full Gauntlet Podcast Index: https://gauntlet-rpg.com/gauntlet-podcast-index.html
You can see the video here: https://youtube.com/watch?v=pGy_puV-BY4
I really liked the video, especially that focusing each session on one singe part of the game, that what playtesters suggest as a solution for a problem isn’t—most of the times—the real solution, to never explain too much but let the playtesters figure it out by themselves, to realize what is your own game mastering and what the game does by itself, to take notes and never be defensive and trying to argue for your solutions.
What I loved was that they said that playtesting is a skill to learn, just like everything else. Both for the playtesters and the game designer.
I cateched on my podcast app, this is really good advice, for testing in general! not only games 
<3