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Pytest Configuration in VS Code

Introduction

This document explains the Pytest configuration for a Python project using VS Code and Poetry. The setup aims to streamline testing, ensure code quality, and enhance developer productivity by leveraging various Pytest plugins and settings.

Default Pytest Configuration

The Pytest configuration in this guide is the default configuration included in the “Cookiecutter Collabora” project. This setup is designed to provide a robust starting point for running tests efficiently and effectively.

We invite you to adapt and customize this configuration to suit your specific project needs and preferences. Modify the settings as needed to optimize your testing workflow and achieve the best results.

Configuration Overview

The Pytest configuration is defined in two key files:

  1. .vscode/settings.json
  2. pyproject.toml

.vscode/settings.json

This file configures Pytest to work seamlessly within VS Code. Below is the configuration used:

{
    "python.testing.pytestArgs": [
        "tests",
        "--cov=src",
        "--cov-report=term-missing",
        "-v",
        "-n",
        "2",
        "--timeout=5"
    ],
    "python.testing.unittestEnabled": false,
    "python.testing.pytestEnabled": true
}

Explanation

  • python.testing.pytestArgs: An array of arguments passed to Pytest when running tests in VS Code.
  • "tests": Specifies the directory where test files are located.
  • "--cov=src": Enables code coverage measurement for the src directory.
  • "--cov-report=term-missing": Displays a coverage report in the terminal, highlighting missing lines.
  • "-v": Enables verbose mode, providing detailed test output.
  • "-n", "2": Utilizes pytest-xdist to run tests in parallel using 2 CPU cores.

  • "--timeout=5": Sets a 5-second timeout for each test to prevent hanging tests.

  • python.testing.unittestEnabled: Disables the unittest framework.

  • python.testing.pytestEnabled: Enables the Pytest framework.

pyproject.toml

This file manages the project dependencies and Pytest settings through Poetry.

[tool.poetry.dev-dependencies]
pytest = "8.2.2"
pytest-benchmark = "4.0.0"
pytest-xdist = "3.6.1"
pytest-cov = "5.0.0"
pytest-mock = "^3.14.0"
pytest-sugar = "1.0.0"
pytest-timeout = "2.3.1"

[tool.pytest.ini_options]
testpaths = ["tests"]
addopts = "-v --cov=src/fpservicesagemodel --cov-report=term-missing -n 2 --timeout=5"
python_files = "test_*.py"
python_classes = "Test*"
python_functions = "test_*"
log_cli = true
log_cli_level = "INFO"
log_format = "%(asctime)s %(levelname)s %(message)s"
log_date_format = "%Y-%m-%d %H:%M:%S"

Explanation

  • [tool.poetry.dev-dependencies]: Specifies the development dependencies required for the project.
  • pytest: The core testing framework.
  • pytest-benchmark: For benchmarking test performance.
  • pytest-xdist: For parallel test execution.
  • pytest-cov: For measuring code coverage.
  • pytest-mock: For mocking objects in tests.
  • pytest-sugar: For a more readable test output.

  • pytest-timeout: For setting time limits on tests.

  • [tool.pytest.ini_options]: Configures Pytest options.

  • testpaths = ["tests"]: Specifies the directory where test files are located.
  • addopts = "-v --cov=src/fpservicesagemodel --cov-report=term-missing -n 2 --timeout=5": Additional options for running tests.
    • "-v": Enables verbose mode.
    • "--cov=src/fpservicesagemodel": Measures coverage for the specified directory.
    • "--cov-report=term-missing": Displays missing coverage in the terminal.
    • "-n 2": Runs tests in parallel using 2 CPU cores.
    • "--timeout=5": Sets a 5-second timeout for each test.
  • python_files = "test_*.py": Pattern for identifying test files.
  • python_classes = "Test*": Pattern for identifying test classes.
  • python_functions = "test_*": Pattern for identifying test functions.
  • log_cli = true: Enables logging to the console during test runs.
  • log_cli_level = "INFO": Sets the log level to INFO.
  • log_format = "%(asctime)s %(levelname)s %(message)s": Specifies the log message format.
  • log_date_format = "%Y-%m-%d %H:%M:%S": Specifies the date format for log messages.

Pre-commit Configuration

To ensure that tests are run automatically before committing or pushing code, you can use the pre-commit framework with the following configuration in your .pre-commit-config.yaml file:

repos:
  - repo: local
    hooks:
      - id: pytest
        name: Run PyTest
        entry: pytest
        language: system
        types: [python]
        stages: [pre-commit, pre-push]
        args: ["tests/"]

Explanation

  • repo: local: Specifies that this hook is defined locally rather than fetched from a remote repository.
  • id: pytest: The unique identifier for this hook.
  • name: Run PyTest: A descriptive name for the hook.
  • entry: pytest: The command to run Pytest.
  • language: system: Indicates that the hook uses system-installed tools.
  • types: [python]: Specifies that this hook should run for Python files.
  • stages: [pre-commit, pre-push]: Defines when the hook should run, here both before commit and before push.
  • args: ["tests/"]: Arguments passed to Pytest, specifying the directory to run tests from.
Why are Pytest extensions under [tool.poetry.dev-dependencies]?

Pytest is primarily used during the development phase of a project and is not intended for use in production or runtime environments. Unit tests, written using Pytest, help developers catch bugs early, facilitate code refactoring, and ensure code quality before deployment.

Running Pytest in production can introduce unnecessary performance overhead and potential security risks. Instead, unit tests are typically executed in CI/CD pipelines to verify code functionality and reliability before the code is deployed to production. This approach ensures that production environments remain optimized for performance and stability.

This is why we include Pytest and its extensions under [tool.poetry.dev-dependencies] in our configuration, ensuring they are available during development but not included in the production environment.

Why Configure Both .vscode/settings.json and pyproject.toml?

Configuring both .vscode/settings.json and pyproject.toml ensures consistent and integrated testing in your development environment.

  • .vscode/settings.json: Customizes Pytest behavior in Visual Studio Code. With the Python extension installed, the beaker icon (flask) appears in the Activity bar, opening the Test Explorer for running and debugging tests directly in VS Code.
  • pyproject.toml: Manages project dependencies and centralizes Pytest configurations for use across different environments.

Conclusion

This configuration ensures that tests are run efficiently and effectively within VS Code, leveraging parallel execution, code coverage, and timeouts to maintain code quality and performance. By following these settings, developers can ensure a consistent and productive testing environment.

See also