path issues when running unit tests

I'm running into trouble when running tests from a directory which is under the project directory.

I have the following folder structure:

project
  /lib1
  /lib2
    source1.py
    source2.py
    /tests
      test_source1.py  

so t=he test I'm trying to run is /project/lib2/tests/test_source1.py,
and it needs to import the module /project/lib2/source1.py


I've tried to set the interpreter working directory by going to:
Edit configurations –> Unittests in test_source1 –>Interperter –> Working directory, and setting it to: /project/lib2/ and then to /project, but still I'm unable to import source1.py in test_source1.py

Please advise,
Boaz