It's not actually the first target in a `.sln` file that is treated as the default startup project, but rather the first fully defined target.
Add a `VS_STARTUP_PROJECT` directory property to specify the project that should be placed first in the `.sln` file so that it will be selected as the default startup project. Co-Author: Taylor Braun-Jones <taylor.braunjones@avigilon.com>
The test will be suitable for covering other `.sln` content too.