Seems like Blizzard is getting ready ensnare even more players with its upcoming Overwatch beta releasing on October 27. It's hard enough to tear myself away from Heroes of the Storm. Like many betas, it's main purpose to to stress test Blizzard servers and to test for any bugs the team might have missed during internal testing. This will be done through two different approaches.
The closed beta will have a small number of players who will be playing the game for the sole purpose of player feedback. It's important for any developer to know what works and what doesn't and smooth things out before the game launches. The first phase of the beta is set to start on October 27 in the Americas with Europe following and Asia's closed beta being deployed at a later date.
The "Beta Test Weekends" will be the times that Blizzard decides to throw as many people at their servers as possible. It's basically common knowledge among gamers that online games will always have server issues the first day a game is released. You can expect the first beta test weekend to be held after BlizzCon. You can sign up for the beta by visiting Blizzards website. Stay tuned for more information about Overwatch as news is made available.