Question

How can I import helper functions in test files without creating packages in the test directory?

Context

I'd like to create a test helper function that I can import in several tests. Say, something like this:

# In common_file.py

def assert_a_general_property_between(x, y):
    # test a specific relationship between x and y
    assert ...


# In test/my_test.py

def test_something_with(x):
    some_value = some_function_of_(x)
    assert_a_general_property_between(x, some_value)

Using Python 3.5, with py.test 2.8.2

Current "solution"

I'm currently doing this via importing a module inside my project's test directory (which is now a package), but I'd like to do it with some other mechanism if possible (so that my test directory doesn't have packages but just tests, and the tests can be run on an installed version of the package, as is recommended here in the py.test documentation on good practices).

my option is to create an extra dir in tests dir and add it to pythonpath in the conftest so.

tests/
    helpers/
      utils.py
      ...
    conftest.py
setup.cfg

in the conftest.py

import sys
import os
sys.path.append(os.path.join(os.path.dirname(__file__), 'helpers'))

in setup.cfg

[pytest]
norecursedirs=tests/helpers

this module will be available with import utils, only be careful to name clashing.