Boeing uses computer analysis and modeling to reduce much of the traditional hands-on flight testing. Most of what flight test pilots do is validation of the computer modeling. Even so, everyone I've met at Boeing who does testing and validation has stellar credentials to include military flight test schools. They tell me the turnover rate is glacial at best.
Boeing has a very mature intern program, have you applied? I'd suggest getting an interview and get the info directly from Boeing.
Boeing: College and Early Career: Engineering Intern Programs