gistfile1.txt

draft $ cat test-pdb.py                                                                                                                                                                  
import sys


def test_something():
    assert 'pdb' not in sys.modules()
draft $ pip-run -q pytest -- -m pytest test-pdb.py                                                                                                                                       
================================================================================== test session starts ==================================================================================
platform darwin -- Python 3.7.2, pytest-4.1.1, py-1.7.0, pluggy-0.8.1
rootdir: /Users/jaraco/draft, inifile:
plugins: xonsh-0.8.8
collected 1 item                                                                                                                                                                        

test-pdb.py F                                                                                                                                                                     [100%]

======================================================================================= FAILURES ========================================================================================
____________________________________________________________________________________ test_something _____________________________________________________________________________________

    def test_something():
>       assert 'pdb' not in sys.modules
E       AssertionError: assert 'pdb' not in {'PyObjCTools': <module 'PyObjCTools' (namespace)>, '__future__': <module '__future__' from '/Library/Frameworks/Pytho.../var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-kwj_l0hg/pytest.py'>, '_abc': <module '_abc' (built-in)>, ...}
E        +  where {'PyObjCTools': <module 'PyObjCTools' (namespace)>, '__future__': <module '__future__' from '/Library/Frameworks/Pytho.../var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-kwj_l0hg/pytest.py'>, '_abc': <module '_abc' (built-in)>, ...} = sys.modules

test-pdb.py:5: AssertionError
=============================================================================== 1 failed in 0.07 seconds ================================================================================