Microsoft announced the Beta 2 Refresh of its Windows Phone SDK 7.1, which it said “represents a month of great progress by the engineering team, further refining and improving the Mango developer experience.” In a blog post, Microsoft’s Cliff Simpkins said that “today’s refresh provides everything you need to update your app for Mango – the tools and the OS image – now.” It will continue to be “refined and finished” moving forward, with the final release due to be available “in the coming month.”

According to Microsoft, the application platform APIs are now locked, meaning that developers can “feel confident to start getting ready” for the Mango apps submission process – which is due to launch next month. It also includes an “initial peek” at a Marketplace Test Kit which will allow developers to test files against the same certification tools used when ingesting apps for the marketplace – it is currently “not fully functional,” but more detail was promised in a future blog post.

Microsoft recently highlighted a number of updates to its App Hub portal for Windows Phone 7 developers, to support availability of Mango. These included the addition of support for more countries, new account management capabilities, and new distribution options.