Testing the tubes

Recently read an article that made me nostalgic for the good olde days. Remember when a radio stopped working and you would pull the back off and take the tubes out? Then you would bring the tubes to an electronics store or even Modell's and test the tubes in a device like that seen in the picture. More often than not, you'd find out you had a bad tube. You'd buy a replacement and you'd be on your way. You had to be careful putting the tubes back in the right slots, though, or the radio might explode.