Where to place utilities in Python unittest test suites?

Question

I am writing unit tests for a largish piece of software written in Python, and there are some tools I wrote to facilitate tests. I would like to continue using these utilities in another test file.

The obvious solution is to put these utilities in a separate file next to the tests and load it, e.g.

import .utilities as tu

but that fails, because

ImportError: attempted relative import with no known parent package

which is fair enough.

So my question is: what is the recommended place to put utilities that are solely used for testing?

Answer 1

Let's say your project's name is coolproj. Assuming that you have the usual structure

coolproj -> coolproj -> __init__.py
                     -> file1.py
                     -> file2.py
                     -> ...
         -> tests -> __init__.py # You need to make `tests` a package!
                  -> utilities.py
                  -> test_file1.py
                  -> test_file2.py
                  -> ...  

Then you can just import your utilities module in, say, test_file1.py via

from tests import utilities

and in the root directory coolproj (where you should be running your testsuite!) you can run all tests using the test discovery feature

python3 -m unittest

This should cover your question. By the way, in case your utilities module is not in tests but in coolproj, then the import should be

from coolproj import utilities

If for some reason you get the message 0 tests run, then you may want to check how exactly you are naming your tests classes and members. In particular, the test discovery feature expects your test modules to be named test_*.py, as exemplified above. Follow the examples in the documentation to name your tests appropriately.