Is video game testing a science career

No, and it's not a "career" I'd recommend. This is because it's a no-skill job with many people looking into it as well. It's not even considered a career, it's a job. It would be hard to find a job because most major companies have their own testers, and the job itself is quite mundane. Though if you really are set on doing this for a living, you have to stick with it and know all the negativity that can come.
If you're really interesting in Video Games being part of your career, be a part of the development of the video game rather than testing it. You also can have more pride and say "I made that game" rather than "I played it before it came out". Besides, if you're part of the development team, you'll do both. And there are multiple different careers for the development of a video game.