How much time is required for testing a video game

This really depends on the video game. Is it Single Player or Multiplayer. Is it single platform or multi-platform.

In the case of console games they dont need as much testing because they are going onto a system they know the exact specs of, with only variations being which console this version is going onto.

However with PC games Testing can last a year or better due to the fact that there are literally thousands of configurations of both hardware and software.

Then there comes multiplayer games which are a whole different ball-park. They have to not only test the client mechanics but also the server configuration and stability. I have seen Multiplayer Online games take 3 years + in testing before they reach release candidate.

All In all there is no one answer for this question. It really depends on the game and moresoe the amount of mechanics built into the game.