Our Ada Software is far from modular. We would have a difficult time converting code pieces of the project for trial testing. How do you suggest we go evualuating Ada-C/C++ Changer to make sure it meets our needs? For example, if we just grabbed 5 random .adb files, would ADA-C/C++ Changer handle the conversion and just tell us what was undefined? Or would it fail completely?

AdaChanger is like a compiler. It requires the "specs" for any package that is "with"ed. It requires the bodies for any generic that is instantiated. It can work on a piece of a program, but that piece must at least include all of the package "spec"s referenced by "with" clauses, directly or indirectly. If you want to "build" an executable, then you will need a self-contained test program, including both specs and bodies for all code. If you simply want to compile the generated C code and/or do a manual review of the generated C code as part of your evaluation, you can get by with just the package specs.