Skippy-Cov

Common errors

• ModuleNotFoundError: No module named 'skippy_cov'

  cause The skippy-cov package is not installed in your current Python environment.
  fix Run `pip install skippy-cov`.

• pytest: error: unrecognized arguments: --skippy-cov

  cause The `skippy-cov` plugin is not being detected by `pytest`. This can happen if it's not installed, there's a version mismatch, or another plugin is interfering.
  fix Ensure `skippy-cov` and `pytest` are installed and up-to-date: `pip install --upgrade skippy-cov pytest`. Verify `pytest --version` shows skippy-cov as a plugin.

• Fatal: not a git repository (or any of the parent directories): .git

  cause Skippy-cov was executed in a directory that is not part of a Git repository. It requires Git for its core functionality.
  fix Initialize a Git repository by running `git init` in your project's root directory or navigate to an existing Git repository.

• FileNotFoundError: [Errno 2] No such file or directory: 'git'

  cause The Git executable is not found in your system's PATH. Skippy-cov directly invokes Git commands.
  fix Install Git on your system and ensure it's accessible from your command line. For Linux: `sudo apt-get install git`, for macOS: `brew install git`, for Windows: download from git-scm.com.

Warnings

• gotcha Skippy-cov requires the project to be a properly initialized Git repository. It relies heavily on Git commands for diffing and file tracking.
  Fix: Ensure you run `git init` in your project root before using skippy-cov, and make sure your changes are committed or staged for diffing.
• gotcha Skippy-cov is a pytest plugin and depends on `pytest` and `coverage.py` being installed in the same environment. Without them, it cannot function correctly.
  Fix: Install all necessary packages: `pip install skippy-cov pytest coverage`.
• breaking In version 0.2.0, skippy-cov changed its pytest integration strategy from `pytest_collection_modifyitems` to `pytest_configure`. This might affect users with highly customized pytest plugins that interact with collection hooks.
  Fix: Review your custom pytest plugins for compatibility. Most standard usage should be unaffected, but complex collection modifications might need adjustment.
• gotcha When using `--skippy-cov` with a diff, it expects a path to a file containing the `git diff` output, not the diff output itself directly or a branch name.
  Fix: Generate the diff into a temporary file first: `git diff main...HEAD -- path/to/file.py > /tmp/my_diff.diff`, then pass the path to the `--skippy-cov` flag: `pytest --skippy-cov=/tmp/my_diff.diff`.

Install

• pip install skippy-cov Install stable version

Quickstart

This quickstart demonstrates how to install skippy-cov, set up a minimal Git repository with a module and tests, run `pytest` to collect initial coverage data, then simulate code changes on a feature branch, and finally use `skippy-cov` with a Git diff to run only the affected tests.

mkdir my_skippy_project && cd my_skippy_project
git init -b main
pip install skippy-cov pytest coverage

# Create a simple module and test file
mkdir src && mkdir src/tests
echo "def func_a():\n    return 'A'\ndef func_b():\n    return 'B'" > src/my_module.py
echo "import pytest\nfrom src.my_module import func_a, func_b\n\ndef test_func_a():\n    assert func_a() == 'A'\n\ndef test_func_b():\n    assert func_b() == 'B'" > src/tests/test_my_module.py
touch src/__init__.py src/tests/__init__.py
git add .
git commit -m "Initial code and tests"

echo "\n--- First run: Collect all coverage data ---"
pytest --skippy-cov --cov=src --cov-report=xml src/tests/

# Simulate a change to func_a and add a new test on a feature branch
git checkout -b feature/new-func
echo "def func_a():\n    return 'A_modified'\ndef func_b():\n    return 'B'\ndef func_c():\n    return 'C'" > src/my_module.py
echo "import pytest\nfrom src.my_module import func_a, func_b, func_c\n\ndef test_func_a():\n    assert func_a() == 'A_modified'\n\ndef test_func_func_b():\n    assert func_b() == 'B'\n\ndef test_func_c():\n    assert func_c() == 'C'" > src/tests/test_my_module.py
git add .
git commit -m "Add func_c and modify func_a"

echo "\n--- Second run: Run only affected tests using diff ---"
# Generate a diff between 'main' branch and current 'feature/new-func' branch
git diff main...feature/new-func -- src/my_module.py > /tmp/my_skippy_diff.diff
pytest --skippy-cov=/tmp/my_skippy_diff.diff src/tests/
echo "Expected: Only tests related to func_a (modified) and func_c (new) should run."