isolation when importing test modules (nose-style)

[pytestbot]

Originally reported by: BitBucket: devtty0, GitHub: devtty0

---

I have a problem with multiple test dirs (find an example attached).

I have the following project structure:

basedir/ 
       /app/__init__.py
              *.py
       tests/__init__.py
               *.py
       core/ /** git submodule **/
              corelib/__init__.py
                         *.py
              tests/*.py

basedir $ PYTHONPATH=.:core:$PYTHONPATH py.test tests core/tests/
================================================================ test session starts =================================================================
platform linux2 -- Python 2.7.3 -- pytest-2.3.4
collected 1 items / 1 errors 

tests/test_id.py .

======================================================================= ERRORS =======================================================================
______________________________________________________ ERROR collecting core/tests/test_sum.py _______________________________________________________
venv/lib/python2.7/site-packages/py/_path/local.py:532: in pyimport
>           __import__(modname)
E           ImportError: No module named test_sum
========================================================= 1 passed, 1 error in 0.05 seconds ==========================================================

basedir $ PYTHONPATH=.:core:$PYTHONPATH py.test tests
================================================================ test session starts =================================================================
platform linux2 -- Python 2.7.3 -- pytest-2.3.4
collected 1 items 

tests/test_id.py .

============================================================== 1 passed in 0.04 seconds ==============================================================

basedir $ PYTHONPATH=.:core:$PYTHONPATH py.test core/tests/
================================================================ test session starts =================================================================
platform linux2 -- Python 2.7.3 -- pytest-2.3.4
collected 1 items 

core/tests/test_sum.py .

============================================================== 1 passed in 0.04 seconds ==============================================================

if i put __init__.py into core directory, py.test works well:

basedir $ touch core/__init__.py
basedir $ ./run_pytest.sh 
================================================================ test session starts =================================================================
platform linux2 -- Python 2.7.3 -- pytest-2.3.4
collected 2 items 

tests/test_id.py .
core/tests/test_sum.py .

============================================================== 2 passed in 0.04 seconds ==============================================================

Nose works fine without __init__.py in core directory:

$ PYTHONPATH=.:core:$PYTHONPATH nosetests tests core/tests/
..
----------------------------------------------------------------------
Ran 2 tests in 0.001s

OK

$ py.test --version
This is py.test version 2.3.4

---

• Bitbucket: https://bitbucket.org/pytest-dev/pytest/issue/268

[pytestbot]

Original comment by Ronny Pfannschmidt (BitBucket: RonnyPfannschmidt, GitHub: RonnyPfannschmidt):

---

this is a tricky interaction of pythonpaths

due to your test layout there are 2 tests packages that are not namespaces

it would require a custom import system to propperly catch that
nose does some magic to keep test modules/packages kind of separate in importing

its up for consideration

[pytestbot]

Original comment by holger krekel (BitBucket: hpk42, GitHub: hpk42):

---

add a note to the documentation that pytest does not mimick nose try to perform "import isolation". Addresses issue268.

[pytestbot]

Original comment by holger krekel (BitBucket: hpk42, GitHub: hpk42):

---

This is really about allowing the same import path to map to different file system paths. This can lead to a number of problems and is the reason, i think, why nose2 dropped it, see https://nose2.readthedocs.org/en/latest/differences.html#test-discovery-and-loading

For now, i regard this issue as an "enhancement" and we may arrive at the conclusion to not support it. Depends also on further feedback.

[RonnyPfannschmidt]

Closing as irrelevant