pytest-mock for enhanced mocking - Framework Patterns

Framework Mode - pytest-mock for enhanced mocking

Folder Structure

test_project/
├── tests/
│   ├── test_example.py
│   ├── test_service.py
│   └── __init__.py
├── src/
│   ├── service.py
│   └── __init__.py
├── conftest.py
├── requirements.txt
└── pytest.ini

This structure separates source code in src/ and tests in tests/. The conftest.py file holds shared fixtures and mocks setup.

Test Framework Layers

• Source Code Layer (src/): Contains application logic to be tested.
• Test Layer (tests/): Contains test cases using pytest and pytest-mock for mocking dependencies.
• Fixtures and Mocks (conftest.py): Central place for reusable pytest fixtures and mock setups using pytest-mock plugin.
• Configuration Layer (pytest.ini): Holds pytest configuration like markers and test options.
• Dependency Management (requirements.txt): Lists pytest and pytest-mock packages.

Configuration Patterns

• pytest.ini: Configure test markers, addopts for verbosity, and test paths.

  [pytest]
  addopts = -v --tb=short
  markers =
      integration: mark test as integration test
      unit: mark test as unit test
  

• conftest.py: Define fixtures for environment setup, mock objects, and shared test data.

  import pytest
  
  @pytest.fixture
  def mock_api_call(mocker):
      return mocker.patch('src.service.api_call')
  

• Environment Variables: Use os.environ or pytest plugins like pytest-env to manage credentials and environment-specific settings.

Test Reporting and CI/CD Integration

• Use pytest built-in reporting with verbose output for clear pass/fail results.
• Integrate with CI/CD pipelines (GitHub Actions, GitLab CI, Jenkins) to run tests automatically on code push.
• Generate JUnit XML reports for CI tools to parse:

  pytest --junitxml=reports/results.xml

• Use pytest plugins like pytest-html for human-readable HTML reports.
• Fail fast option --maxfail=1 can be used to stop on first failure during CI runs.

Best Practices

1. Use pytest-mock fixture: Use the mocker fixture from pytest-mock to patch dependencies cleanly and restore them automatically after tests.
2. Isolate tests: Mock external calls and side effects to keep tests fast and reliable.
3. Centralize mocks: Define common mocks in conftest.py to avoid duplication and improve maintainability.
4. Use descriptive test names and markers: Helps organize and selectively run tests.
5. Keep tests independent: Avoid shared state between tests to prevent flaky results.

Self Check

Where in this framework structure would you add a new mock for an external API call used in multiple tests?

Key Result

Use pytest-mock's mocker fixture in conftest.py to create reusable, clean mocks for isolated and maintainable tests.