Even this last one where it was really smooth - people didn't have long queues leading into getting into the experience - we still found things happening in the back end that if left unresolved, would have resulted in some issues during the launch experience. That's entirely the purpose of the betas we did. Everything has been about, we need data to make sure the launch goes smooth. 'These are not marketing betas,' Piepiora said.

Reiterating comments Diablo development chief Rod Fergusson made to Eurogamer in March, Piepiora said these tests are designed to help Blizzard prepare Diablo 4 for launch, and should not be considered marketing betas. And with each of those we found lots of little things that happen, like this happens with clan invitations, this happens when you join a party in a certain way - lots of little things like that across the board.' 'When you have people coming through different ISPs and coming in through different servers around the world, there's so much more data you get from that. While Blizzard has learned a great deal from these internal tests, there's no substitute for live player tests, Piepiora said. Piepiora revealed Blizzard has run internal testing on Diablo 4 for well over a year, spinning up servers with millions of automated accounts creating basic actions such as finding a piece of gear and equipping it, to killing a monster and starting a party with another robot. Newscast: After Redfall's launch woes, where next for Xbox? 'Every one of these betas has been transformational in terms of our understanding of our own technical capacity and what we need to do to make that a smoother launch experience in general,' Piepiora said. Speaking to Eurogamer in an interview in London today, Diablo 4 art director John Mueller and associate game director Joe Piepiora said Blizzard is feeling good about the launch because it had learned so much from the various tests. The event seemed to go smoothly, with most players reporting little to no queue time and, when in-game, improved performance compared to that seen in previous tests. The developer held a 'Server Slam' event over the weekend to test the upcoming action role-playing game's servers one final time ahead of launch in June.

Blizzard has said it's feeling 'really confident' Diablo 4 will enjoy a smooth launch following a series of server stress tests.

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