Writing Makefile to separate tests from source code in Python

I'm working on a project and have all of my source code in a subdirectory called src/. I've written a bunch of tests (this is all in Python, by the way) that require importing files that are in src/. Ideally, I'd like to have a separate subdirectory tests/ at the same level as src/ so that I can store my tests there instead. Unfortunately, the test files need to be in the same subdirectory as the source files to import them under this scheme. I know that this can be achieved using a Makefile, but am not too sure on how to write that. Could anyone help me out? I believe that you just need to change the file path.