Web Application Testing

Comprehensive test automation covering unit, integration, and E2E testing.

Test Types

Best Practices

• Test behavior, not implementation
• One assertion per test for clarity
• AAA pattern: Arrange, Act, Assert
• Create test data factories
• Mock external dependencies appropriately

Playwright E2E Testing

Decision Tree

Static HTML? → Read HTML for selectors → Write script
Dynamic? → Server running? → No → Start it in the background (e.g. `npm run dev &`) and wait for its port
                           → Yes → Navigate → wait for the content under test → Screenshot → Identify selectors → Execute

Template

from playwright.sync_api import sync_playwright

with sync_playwright() as p:
    browser = p.chromium.launch(headless=True)
    page = browser.new_page()
    page.goto('http://localhost:5173')
    page.get_by_role('main').wait_for()  # wait on the content under test, not 'networkidle'
    # ... test logic
    browser.close()

TDD Workflow

1. Identify affected test files after code changes
2. Run tests: npm test or pytest
3. On failure: Parse errors, distinguish legitimate failure vs outdated expectations vs environment
4. Fix: Preserve original intent, update expectations only for legitimate changes, never weaken tests to pass

Common Pitfalls

• Don't inspect the DOM of a dynamic app before the content you need has rendered. Wait on that element (expect(locator).to_be_visible()), not on networkidle, which Playwright's docs discourage for tests
• Don't use flaky selectors that change
• Do use descriptive selectors: text=, role=, IDs

Quality Gates

• All tests passing before merge
• Coverage maintained or improved
• No skipped tests without justification
• E2E tests cover critical user journeys
• Tests run in <10 minutes total