It looks like it only tests small octal tubes, and it doesn't say what is tested--transconductance, emission, noise? These small tubes are the type I would just have spares and I would "test" the tube by occasionally swapping in the spares to see if the sound improves.
I do own a tube tester, which I have lent to a friend who has more uses for it, but, it is quite a bit more expensive than the model you show (it is an Amplitrex), and can test many tube types, including those with grid caps like the tubes I run.
I do own a tube tester, which I have lent to a friend who has more uses for it, but, it is quite a bit more expensive than the model you show (it is an Amplitrex), and can test many tube types, including those with grid caps like the tubes I run.