Plone Testing Best Practices

Testing is crucial for Plone development. It ensures your code works as expected. Good tests save time and reduce bugs.

This guide covers best practices for writing unit and integration tests in Plone. Follow these tips to improve your test quality.

Why Testing Matters in Plone

Tests verify your code behaves correctly. They catch errors early. This prevents bugs in production.

Plone's complex architecture needs thorough testing. Components like workflows, views, and content types must work together. Our Plone Workflow Customization Guide shows why testing workflows is essential.

Unit Testing Basics

Unit tests check small code units in isolation. They're fast and focused. Each test should verify one behavior.

Use Plone's testing infrastructure. It provides useful base classes and helpers. Always inherit from PloneTestCase for unit tests.

from Products.CMFPlone.testing import PLONE_FIXTURE
from plone.app.testing import PloneSandboxLayer
from plone.app.testing import applyProfile

class MyLayer(PloneSandboxLayer):
    defaultBases = (PLONE_FIXTURE,)
    
    def setUpZope(self, app, configurationContext):
        # Load ZCML
        import my.package
        self.loadZCML(package=my.package)

Writing Good Unit Tests

Follow these principles for effective unit tests:

1. Test one thing per test method. Keep tests small and focused.

2. Use descriptive test names. They should explain what's being tested.

3. Mock external dependencies. Isolate the code under test.

Here's an example test for a content type:

def test_document_creation(self):
    """Test document creation with required fields"""
    portal = self.layer['portal']
    portal.invokeFactory('Document', 'doc1', title='Test Doc')
    self.assertEqual(portal['doc1'].title, 'Test Doc')

Integration Testing in Plone

Integration tests check how components work together. They're slower but more realistic than unit tests.

Use Plone's integration testing layer. It sets up a complete Plone site. This is perfect for testing views and workflows.

For complex UI components like Custom Volto Blocks, integration tests are essential.

Best Practices for Integration Tests

1. Test complete user scenarios. Simulate real usage.

2. Check interactions between components. Verify data flows correctly.

3. Use realistic test data. Mimic production content.

Example integration test for a view:

def test_view_rendering(self):
    """Test custom view renders correctly"""
    portal = self.layer['portal']
    view = portal.restrictedTraverse('@@my-view')
    result = view()
    self.assertIn('Expected content', result)

Test Organization and Structure

Keep your tests well organized. Follow these guidelines:

1. Mirror your package structure. Keep tests near the code they test.

2. Separate unit and integration tests. Use different folders or markers.

3. Use test fixtures wisely. Share setup code between tests.

For complex systems like Plone Catalog, proper test organization is critical.

Test Data Management

Good test data makes tests reliable. Follow these tips:

1. Create minimal test data. Only what's needed for the test.

2. Clean up after tests. Don't leave modified state.

3. Use factories for complex objects. Keep test code DRY.

def setUp(self):
    """Create test content before each test"""
    self.portal = self.layer['portal']
    self.portal.invokeFactory('Folder', 'test-folder')
    self.folder = self.portal['test-folder']

Testing Edge Cases

Don't just test happy paths. Check error conditions too. Test invalid inputs and permissions.

Example permission test:

def test_unauthorized_access(self):
    """Test view blocks unauthorized users"""
    from zExceptions import Unauthorized
    with self.assertRaises(Unauthorized):
        self.folder.restrictedTraverse('@@protected-view')

Continuous Integration

Run tests automatically on changes. Use CI tools like GitHub Actions or Travis CI.

Configure test coverage reporting. Aim for at least 80% coverage.

Run tests against multiple Plone versions. Ensure compatibility.

Debugging Failed Tests

When tests fail:

1. Read the error message carefully. It often explains the problem.

2. Check test setup. Missing dependencies are common issues.

3. Use pdb for complex failures. Inspect runtime state.

Conclusion

Good testing is key to robust Plone development. Follow these best practices for reliable tests.

Start with unit tests for isolated components. Add integration tests for complete scenarios. Keep tests clean and well-organized.

For more advanced topics, see our Plone Event Systems Guide. Happy testing!