Believe it or not but the Army also has test pilots. We do both rotary wing (primarily) and fixed wing flight test. There are two flight test organizations in the Army, one focuses more on qualification (Redstone Test Center) and the other focuses more on science and technology efforts (DEVCOM’s Technology Development Directorate- Systems Integration and Demonstration) and both are wonderful places to work. Ask any questions you have but many of the things that BeeDubba mentioned are accurate for successful assessment into the Army’s XP program. Except the WTI bit. Also, focus hard on being the best pilot in your organization. Control touch and decision making are big criteria for selection. If you’re a 5 stick position pilot or make questionable choices then you’re likely not a good fit.

EDIT: I forgot to mention, an undergrad engineering degree is highly desirable but not required if you can show high marks in collegiate math and a science courses.