Where do the Python unit tests go? [closed]

For a file module.py, the unit test should normally be called test_module.py, following Pythonic naming conventions.

There are several commonly accepted places to put test_module.py:

1. In the same directory as module.py.
2. In ../tests/test_module.py (at the same level as the code directory).
3. In tests/test_module.py (one level under the code directory).

I prefer #1 for its simplicity of finding the tests and importing them. Whatever build system you're using can easily be configured to run files starting with test_. Actually, the default unittest pattern used for test discovery is test*.py.

Only 1 test file

If there has only 1 test files, putting it in a top-level directory is recommended:

module/
    lib/
        __init__.py
        module.py
    test.py

Run the test in CLI

python test.py

Many test files

If has many test files, put it in a tests folder:

module/
    lib/
        __init__.py
        module.py
    tests/
        test_module.py
        test_module_function.py

# test_module.py

import unittest
from lib import module

class TestModule(unittest.TestCase):
    def test_module(self):
        pass

if __name__ == '__main__':
    unittest.main()

Run the test in CLI

# In top-level /module/ folder
python -m tests.test_module
python -m tests.test_module_function

Use unittest discovery

unittest discovery will find all test in package folder.

Create a __init__.py in tests/ folder

module/
    lib/
        __init__.py
        module.py
    tests/
        __init__.py
        test_module.py
        test_module_function.py

Run the test in CLI

# In top-level /module/ folder

# -s, --start-directory (default current directory)
# -p, --pattern (default test*.py)

python -m unittest discover

Reference

• pytest Good Practices for test layout
• unittest

Unit test framework

• nose
• nose2
• pytest

A common practice is to put the tests directory in the same parent directory as your module/package. So if your module was called foo.py your directory layout would look like:

parent_dir/
  foo.py
  tests/

Of course there is no one way of doing it. You could also make a tests subdirectory and import the module using absolute import.

Wherever you put your tests, I would recommend you use nose to run them. Nose searches through your directories for tests. This way, you can put tests wherever they make the most sense organizationally.

We had the very same question when writing Pythoscope (https://pypi.org/project/pythoscope/), which generates unit tests for Python programs. We polled people on the testing in python list before we chose a directory, there were many different opinions. In the end we chose to put a "tests" directory in the same directory as the source code. In that directory we generate a test file for each module in the parent directory.

I also tend to put my unit tests in the file itself, as Jeremy Cantrell above notes, although I tend to not put the test function in the main body, but rather put everything in an

if __name__ == '__main__':
   do tests...

block. This ends up adding documentation to the file as 'example code' for how to use the python file you are testing.

I should add, I tend to write very tight modules/classes. If your modules require very large numbers of tests, you can put them in another, but even then, I'd still add:

if __name__ == '__main__':
   import tests.thisModule
   tests.thisModule.runtests

This lets anybody reading your source code know where to look for the test code.