I'm not sure I understand it very well, but those two sites are quite
convincing that there should not be __init__.py inside testing/
directory.
[1] says:
avoid “__init__.py” files in your test directories. This way your
tests can run easily against an installed version of mypkg,
independently from the installed package if it contains the tests or
not.
[2] says:
installed-versus-checkout version. py.test collects test modules on
the filesystem and then tries to import them under their fully
qualified name. This means that if your test directory contains an
init__.py file then your py.test invocation may end up importing the
package from the checkout directory rather than the installed package.
Therefore it is better to try to avoid init__.py files in test
directories and also try to avoid custom PYTHONPATH settings. After
all, it is the job of your setup.py file and the install tools to care
for making the package properly available for importing.
[1] https://pytest.org/latest/goodpractises.html#choosing-a-test-layout-import-rules
[2] http://tox.readthedocs.org/en/0.9/example/pytest.html