# Dj2695 Custom Copilot Python Testing > Python Testing Skill - Skill: `tomevault-io/dj2695-custom-copilot-python-testing` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/dj2695-custom-copilot-python-testing` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/dj2695-custom-copilot-python-testing/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/dj2695-custom-copilot-python-testing --- # Python Testing Skill Comprehensive testing patterns for Python applications using pytest, including services, repositories, and Firebase Cloud Functions. ## When to Use This Skill - Writing unit tests for Python code - Testing service and repository layers - Testing Firebase Cloud Functions - Setting up pytest fixtures and mocks - Writing integration tests - Configuring test coverage with pytest-cov - Implementing TDD workflow ## Prerequisites ```bash pip install pytest pytest-cov pytest-mock pytest-asyncio pip install firebase-functions-test # For Firebase Functions ``` ## Test Types Overview | Type | Location | Command | Coverage Target | |------|----------|---------|-----------------| | Unit | `tests/unit/` | `pytest tests/unit/` | 80%+ | | Integration | `tests/integration/` | `pytest tests/integration/ --integration` | Key flows | | Service | `tests/unit/services/` | `pytest tests/unit/services/` | 80%+ | | Repository | `tests/unit/repositories/` | `pytest tests/unit/repositories/` | 80%+ | | Firebase Functions | `functions/tests/` | `pytest functions/tests/` | 100% for auth/security | ## Quick Start ### Basic Test Structure ```python # tests/test_calculator.py import pytest def test_addition(): """Test that addition works correctly.""" assert 1 + 1 == 2 def test_division_by_zero(): """Test that division by zero raises error.""" with pytest.raises(ZeroDivisionError): 1 / 0 ``` ### Running Tests ```bash # Run all tests pytest # Run with verbose output pytest -v # Run specific file pytest tests/test_calculator.py # Run with coverage pytest --cov=. --cov-report=html # Run only unit tests pytest -m unit # Run integration tests pytest -m integration --integration ``` ## Testing Patterns ### Unit Tests Fast, isolated tests for single units of functionality. See [references/PYTEST.md](references/PYTEST.md) for comprehensive patterns. ```python import pytest from my_module import Calculator class TestCalculator: @pytest.fixture def calculator(self): return Calculator() def test_add(self, calculator): assert calculator.add(2, 3) == 5 ``` ### Service Tests Test business logic orchestration. Services coordinate between repositories and external services. ```python from unittest.mock import Mock import pytest class TestUserService: @pytest.fixture def mock_repository(self): return Mock() @pytest.fixture def service(self, mock_repository): return UserService(repository=mock_repository) def test_create_user_success(self, service, mock_repository): mock_repository.create.return_value = "user-123" result = service.create_user({"email": "test@example.com"}) assert result == "user-123" ``` ### Repository Tests Test data access layer. Mock database clients to avoid external dependencies. ```python def test_repository_get_by_id(mock_firestore): repository = UserRepository(mock_firestore) mock_firestore.collection().document().get().to_dict.return_value = {"id": "123"} result = repository.get_by_id("123") assert result["id"] == "123" ``` ### Firebase Functions Tests Test Cloud Functions with `firebase-functions-test`. See [references/FIREBASE-FUNCTIONS.md](references/FIREBASE-FUNCTIONS.md) for details. ```python from firebase_functions import https_fn from unittest.mock import Mock import pytest def test_function_requires_auth(): req = Mock(spec=https_fn.CallableRequest) req.auth = None with pytest.raises(https_fn.HttpsError) as exc_info: my_function(req) assert exc_info.value.code == "unauthenticated" ``` ## Common Fixtures ### Setup in conftest.py ```python # conftest.py import pytest from unittest.mock import Mock @pytest.fixture def mock_firestore_client(): """Mock Firestore client for tests.""" return Mock() @pytest.fixture def test_user_id(): """Standard test user ID.""" return "test-user-123" @pytest.fixture def sample_user_data(): """Sample user data for tests.""" return { "id": "user-123", "email": "test@example.com", "created_at": "2024-01-01T00:00:00Z" } ``` See [references/PYTEST.md](references/PYTEST.md) for advanced fixture patterns. ## Test Organization ``` backend/ ├── functions/ │ ├── main.py │ └── tests/ │ ├── conftest.py │ ├── test_auth_functions.py │ └── test_data_functions.py └── tests/ ├── conftest.py ├── unit/ │ ├── services/ │ │ └── test_user_service.py │ └── repositories/ │ └── test_user_repository.py └── integration/ └── test_user_flow.py ``` ## Custom Markers ```python # pytest.ini [pytest] markers = unit: Unit tests integration: Integration tests slow: Slow-running tests security: Security-related tests # Usage in tests @pytest.mark.unit def test_fast_unit(): assert True @pytest.mark.integration def test_integration(): assert True ``` Run specific markers: ```bash pytest -m unit pytest -m "integration and not slow" ``` ## TDD Workflow ``` 1. Write failing test → Define expected behavior → Run test, should fail (RED) 2. Implement minimum code to pass → Write simplest implementation → Run test, should pass (GREEN) 3. Refactor → Improve code quality → Keep tests passing 4. Repeat ``` ## Templates Available | Template | Purpose | Location | |----------|---------|----------| | `unit-test.py.template` | Basic unit tests | `templates/` | | `service-test.py.template` | Service layer tests | `templates/` | | `repository-test.py.template` | Repository pattern tests | `templates/` | | `function-test.py.template` | Firebase callable function tests | `templates/` | | `conftest.py.template` | Shared fixtures and configuration | `templates/` | ### Using Templates 1. Copy template to your test directory 2. Replace placeholders: - `${ClassName}` → Your class name (PascalCase) - `${module_name}` → Your module name (snake_case) - `${ServiceName}` → Your service name 3. Adjust imports and test cases 4. Run tests to verify ## Rules ✅ **DO:** - Test behavior, not implementation - Use mocks for external dependencies - Cover success AND failure paths - Write descriptive test names - Keep unit tests fast (<100ms) - Use fixtures for setup/teardown - Organize tests by type (unit/integration) ❌ **DON'T:** - Write tests that always pass - Test private methods directly - Mock the class under test - Skip error path testing - Put integration tests with unit tests - Hardcode test data in multiple places ## Further Reading - [references/PYTEST.md](references/PYTEST.md) - Advanced pytest patterns, fixtures, parametrization - [references/FIREBASE-FUNCTIONS.md](references/FIREBASE-FUNCTIONS.md) - Firebase Functions testing specifics - [references/INTEGRATION.md](references/INTEGRATION.md) - Integration testing patterns --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/dj2695) — claim your Tome and manage your conversions.