This isn't my exact area either, so my terminology is probably off, but one way to do this would be to compile the "backend" code separately and run unit tests

This isn't my exact area either, so my terminology is probably off, but one way to do this would be to compile the "backend" code separately and run unit tests on that. Treat it as a library in your application, if you will. Another approach I've heard used was just faking the library from the headers - as long nothing from it is called in the course of your testing, your program wouldn't notice.