I fixed the issue that test_old and test_utils was failing test from pytest.
I added the init.py file in orbitdeterminator folder and doppler folder. This eventually fixed the problem with test_utils.
Then I had to change the name of import from orbdet to orbitdeterminator.doppler which eventually fixed the issue with test_old.
I believe this error is not due to something that I have changed. It has run appropriately in my machine.
Please check if it runs accurately in your machine.
I fixed the issue that test_old and test_utils was failing test from pytest. I added the init.py file in orbitdeterminator folder and doppler folder. This eventually fixed the problem with test_utils. Then I had to change the name of import from orbdet to orbitdeterminator.doppler which eventually fixed the issue with test_old.