CA Django Testing Skill

CA Django Testing Skill

This skill helps write and run Django unit tests in Consumer Affairs repositories with a focus on achieving 100% code coverage.

When to Use This Skill

AUTOMATIC ACTIVATION TRIGGERS - Activate this skill immediately when:

• ✅ User mentions ANY coverage-related terms: "coverage", "codecov", "test coverage", "partial coverage", "branch coverage", "uncovered lines", "missing coverage", "BrPart", "line X is not covered", "partially covered"
• ✅ User asks to write tests for CA repository code
• ✅ User wants to add test coverage for existing functions
• ✅ User needs to run tests in CA repos
• ✅ User mentions fixing test failures or improving coverage
• ✅ User references specific test files or test paths in CA repos
• ✅ User says "use the test skill" or similar phrases

PROACTIVE USE - Also use this skill proactively (without being asked) when:

• After implementing new features in CA repos that need tests
• After fixing bugs in CA repos that need test verification
• When analyzing code that lacks proper test coverage

Writing Tests

Test File Location Strategy

CRITICAL: Always prioritize using existing test modules unless creating a new code module:

1. Check for existing test files first before creating new ones
2. Add tests to existing test modules that are related to the code being tested
3. Only create new test files when:
   • Creating a completely new code module
   • The existing test file would become too large (>1000 lines)
   • The new functionality is logically separate from existing tests

Test Structure Requirements

All tests MUST follow these principles:

1. Test base class

Some repositories might have their own baseclass extending Django's TestCase class.

• Look for other test modules and make sure you're using the same base class as they
• If you don't find test modules examples, try finding if we're extending Django's base TestClass with our own

2. Unit Test Each Function Separately

• Each function/​method should have its own test class
• Test one function at a time in isolation
• Use mocking for dependencies and external calls

3. Cover Every Code Path

THIS IS CRITICAL: You must write tests for:

• ✅ Happy path (expected inputs)
• ✅ Edge cases (empty inputs, None values, boundary conditions)
• ✅ Error conditions (exceptions, invalid inputs)
• ✅ Each branch in if/​else statements
• ✅ Each iteration scenario in loops
• ✅ Each return statement path
• ✅ Early returns and guard clauses

Goal: 100% code coverage - codecov must pass in CI

4. Test Naming Convention

def test_<function_name>_<scenario>_<expected_outcome>(self):
    """Clear description of what is being tested"""

Examples:

• test_calculate_total_with_valid_items_returns_sum()
• test_calculate_total_with_empty_list_returns_zero()
• test_calculate_total_with_negative_values_raises_error()

Testing Best Practices

Use Mocking Appropriately

from unittest.mock import patch, Mock, MagicMock

class MyServiceTestCase(TestCase):
    @patch('app.module.external_api_call')
    def test_service_with_mocked_api(self, mock_api):
        mock_api.return_value = {'status': 'success'}
        # Test your code

Use Fixtures and Setup

class MyTestCase(TestCase):
    def setUp(self):
        """Set up test fixtures that are reused across tests"""
        self.user = User.objects.create(username='testuser')

    def tearDown(self):
        """Clean up after tests if needed"""
        pass

Test Database Interactions

from django.test import TestCase

class ModelTestCase(TestCase):
    def test_model_creation(self):
        instance = MyModel.objects.create(field='value')
        self.assertEqual(instance.field, 'value')
        self.assertIsNotNone(instance.pk)

Running Tests

Priority Order for Running Tests

Use the ca helper script with the following priority:

1. First Try: ca magictest (PREFERRED)

ca magictest path.to.the.tests.folder.or.module

Examples:

• ca magictest app.api.tests.test_views
• ca magictest app.api.tests
• ca magictest . (run all tests)

This is the preferred method - it uses containers that are already running.

2. If magictest fails: ca pytest

ca pytest path/​to/​the/​tests/​folder/​or/​module

Use this if the repo has pytest support:

• ca pytest app/​api/​tests/​test_views.py
• ca pytest app/​api/​tests/

3. If pytest not available: ca test

ca test path.to.the.tests.folder.or.module

Fallback to Django's test runner:

• ca test app.api.tests.test_views

IMPORTANT: Container Usage

• DO NOT use docker compose run - this starts a separate container
• DO USE the ca script - it uses already running containers
• The containers should already be running before executing tests

Running Specific Tests

To run a single test method:

ca magictest app.api.tests.test_views.MyTestCase.test_specific_method

Workflow Example

When user asks to "write tests for the authenticate function":

1. Locate the function to understand its code paths

2. Find existing test file for that module (e.g., if function is in app/​api/​auth.py, look for app/​api/​tests/​test_auth.py)

3. Analyze all code paths in the function:

   • Note all branches (if/​else, try/​except)
   • Note all return statements
   • Note edge cases

4. Write comprehensive tests covering each path:

   • Create test class for the function
   • Write individual test methods for each code path
   • Use mocking for external dependencies

5. Run tests using ca magictest:

   ca magictest app.api.tests.test_auth
   

6. Verify coverage - ensure all lines are covered

7. Fix any failures and re-run

Coverage Requirements

• Target: 100% code coverage
• Every line of code must be executed by at least one test
• Every branch must be tested
• Codecov CI check must pass
• Use coverage reports to identify untested code paths

Common Patterns in CA Repos

Testing API Views

from django.test import TestCase, RequestFactory
from unittest.mock import patch

class ViewTestCase(TestCase):
    def setUp(self):
        self.factory = RequestFactory()

    def test_view_returns_200(self):
        request = self.factory.get('/​api/​endpoint/')
        response = my_view(request)
        self.assertEqual(response.status_code, 200)

Testing with Authentication

from django.contrib.auth.models import User

class AuthenticatedTestCase(TestCase):
    def setUp(self):
        self.user = User.objects.create_user(
            username='testuser',
            password='testpass'
        )
        self.client.login(username='testuser', password='testpass')

Testing Async Code

from django.test import TestCase
import asyncio

class AsyncTestCase(TestCase):
    def test_async_function(self):
        result = asyncio.run(my_async_function())
        self.assertEqual(result, expected_value)

Remember

✅ Check for existing test files first ✅ Cover every single code path ✅ Use ca magictest for running tests ✅ Aim for 100% coverage ✅ Mock external dependencies ✅ Test error conditions, not just happy paths ✅ Use descriptive test names ✅ Keep tests focused and isolated