Test for import of optional dependencies in __init__.py with pytest: Python 3.5 /3.6 differs in behaviour

Question

I have a package for python 3.5 and 3.6 that has optional dependencies for which I want tests (pytest) that run on either version.

I made a reduced example below co

Answer 1

import sys
from unittest.mock import patch

def test_without_dependency(self):
    with patch.dict(sys.modules, {'optional_dependency': None}):
        # do whatever you want

What the above code does is, it mocks that the package optional_dependency is not installed and runs your test in that isolated environment inside the context-manager(with).

Keep in mind, you may have to reload the module under test depending upon your use case

import sys
from unittest.mock import patch
from importlib import reload

def test_without_dependency(self):
    with patch.dict(sys.modules, {'optional_dependency': None}):
        reload(sys.modules['my_module_under_test'])
        # do whatever you want