Using Python's `unittest` module to compose tests of functions in a separate file

Question

I have an issue with getting my unit tests to resolve calls to the S.U.T.'s functions. The S.U.T. is defined in a separate file, but in the same project. I've considerable Python experience, but I've never tried to deploy code in a conventional way (which generally suggests conventional testing). The directory structure I'm using seems to be in line with PyPI convention, but I'm missing the step on executing unit tests.

Note 1: I have tried reviewing the official unittest module's API documentation & tutorials, as well as some unofficial docs. There's not a lot bridging the gap between new, undeployed project and downloading projects already deployed.

Note 2: I'm not interested in using any third-party unit testing framework. I'd like to stick to unittest module and its conventions. I'm hoping to keep the original project as cross-platform and third-party dependency-light as possible.

Note 3: Adding import mfut or from mfut import conditionallyClose statements to all_tests.py results in ModuleNotFoundError: No module named 'mfut'. I'm sure this has something to do with the PYTHONPATH, but changing that environment variable strikes me as fragile. I'm hoping there's a more robust way.

Below is merely an example toy problem, but the test cases for the original project aren't much more sophisticated.

---

Given the following Python 3 project directory structure:

My Fun Unit Testing
    ├───src
    │   └───mfut
    │       └───mfut.py
    │
    └───tests
        └───all_tests.py

and the following contents of file mfut.py:

import math
def conditionallyClose(x1, x2):
    if math.abs(x1) < 1:
        return math.isclose(x1, x2)
    if math.abs(x1) < 1e6:
        return math.isclose(x1, x2, rel_tol=0.10)
    return math.isclose(x1, x2, rel_tol=0.001)

and the following contents of all_tests.py:

from unittest import TestCase
from math import inf
class onlyTestCase(TestCase):
    def testConditionallyClose_mag1(self):
        self.assertTrue(conditionallyClose(0.05, 0.06))

    def testConditionallyClose_mag6(self):
        self.assertTrue(conditionallyClose(1200000, 1085000))

    def testConditionallyClose_magInf(self):
        self.assertTrue(conditionallyClose(inf, inf))

what is the Python 3 convention (or requirement) for getting the conditionallyClose(...) calls in all_tests.py to resolve?

Answer 1

The reason for your error is that python cannot recognize any library with the name mfut. If you import it like this from mfut import conditionallyClose, it must be either a library, or a file in the same directory as your current python file.

To solve this problem, take these steps:

1. First of all make sure that your project file structure is like this:

2. Create a setup.py file for you project (you can also use PyCharm to do it) and put it in the root directory of you project (which in this case is "B:\Repos\SampleProject").

3. Activate your virtual environment and run pip install -e . in the root of you project directory. This will use the setup.py and make python run your code as a python library and refer to the code dynamically from your files.

4. Now you can import your code like this from any file:

   from src.mfut.mfut import conditionallyClose