How to Solve 'ImportError: No module named...' Issues in pytest Due to Path Problems?

PATH Issues with pytest: "ImportError: No module named..."

When using pytest, it is common to encounter ImportError exceptions due to path issues. This can be especially prevalent in different operating systems and project structures. Let's address this issue and explore potential solutions.

Conftest Solution (pytest < 7)

One effective way to address path issues is by utilizing a conftest.py file. Pytest searches for conftest modules during test collection to gather custom hooks and fixtures. By placing an empty conftest.py file in the root directory of your project (where you run pytest), pytest automatically adds the parent directory to sys.path, making your application modules available for import.

Example:

For a project structure like this:

repo/
   |--app.py
   |--settings.py
   |--models.py
   |--tests/
          |--test_app.py

Simply add an empty conftest.py file to the repo/ directory.

Pythonpath Setting (pytest >= 7)

For recent versions of pytest (7 and above), a more convenient solution is to utilize the pythonpath setting. This allows you to modify sys.path directly through the pytest configuration. In your pyproject.toml or pytest.ini file, add the following:

[tool.pytest.ini_options]
pythonpath = ["."]

This is a cleaner approach that does not require any custom code or manipulation of sys.path.

Other Considerations

Project Structure: Adjust the placement of the conftest.py file or pythonpath configuration based on your project structure. For instance, in a typical src-based layout, place conftest.py in the src directory, not the root.

src Layout: Be cautious when adding src to PYTHONPATH. It can undermine the benefits of using a src layout, as you end up testing the repository code rather than the installed package.

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