The process was ok, applied on StackOverflow. Got an email to discuss with recruiter, about 1 hour on previous experience and typical HR questions, strengths, weaknesses etc. Second stage was to develop a UWP app using thier API and responsive to screen width. The problem was a good one cause it allowed you show all aspects of WP development. Ultimately didn't make it to next step as I did not use any architecture to develop app like MVP and didn't show a deep enough understanding of OOP SOLID principles.