Work on Windows Phone 10 is already underway, but Microsoft hasn't yet provided any sort of details about the upcoming operating system, even though everyone expects the new release to change the smartphone platform from the ground up.

Windows Phone 10 is expected to see daylight at about the same time as Windows 10 in spring 2015, and according to a new report, the first testing builds have already been submitted to partners to see how this one works on new devices.

A report by WinFuture reveals that partners who received this early testing version of Windows Phone 10 actually got their hands on an old build that doesn't bring too many changes in terms of aesthetics, but it is mostly focused on changes under the hood.

Needless to say, no leaks are available right now, as Microsoft most likely individually signed each of these builds in order to make sure that no one publishes them online.

Windows Phone 10 name not yet confirmed

Even though everybody expects Microsoft to call the upcoming smartphone operating system Windows Phone 10, people close to the matter suggest a possible name change that would actually revamp the platform altogether and bring it in line with the other versions of Windows currently on the market.

Sources indicate that Microsoft could rename Windows Phone to just Windows in order to bring more people on board, but this is clearly a risky decision, especially when thinking about the confusion that could be created following such a strategy.

The testing builds that are currently submitted to partners are called Windows Phone 10, but this doesn't mean anything right now, especially since we're still in the very early development stages of the new OS.

Preview coming in early 2015

Since Microsoft has already started work on Windows Phone 10 and is now shipping early builds to partners, but users might actually get the very first preview version in early 2015, if development goes according to the plan.

Windows 10 Technical Preview, which is the desktop version of the upcoming operating system, is now under development at Microsoft and the next build is scheduled to arrive in early 2015 as well, which makes some people believe that the company plans to introduce this update and the first public preview of Windows Phone 10 at the same time.

Obviously, these are really vague details and nobody can tell for sure if these plans are true or not, so don't take anything for granted until Microsoft actually confirms this.