How old do you have to be to work as a video game tester?
It all depends on where you live, and what your level of expertise is in certain areas.
In some places the legal age requirement is 16, and others it's 18, and some are in the middle. This number all depends on where you live.
Now, to get hired as a video game tester they want you to have some level of experience with not only just "gaming," but also to have a degree of some sorts in programming (Or at least a fair amount of experience).
Keep in mind that being a video game tester is not an easy job, and it can tend to get very monotonous. You may have to play a certain portion of a game over 200 times, taking notes every time. And not to mention the version of the game you will be playing may be extremely unbalanced, and it will detract from the fun of playing actual video games.
If you are serious about wanting to become a video game tester my recommendation is to get a degree in Computer Programming, and have a dire passion for video games, and be over 18. If you meet all those prerequisites, you are eligible to become a video game tester. Of course, you still have to get hired.