Page 20 - Testing/E2E

Testing responsive layouts by randomly trying dozens of viewport widths wastes test time and still misses the spots that matter. Bugs almost always appear exactly at the breakpoint boundaries defined in your Tailwind design system, precisely where navigation, grid columns, and font sizes switch. Targeted boundary tests in Cypress and Playwright secure exactly these transitions automatically and reliably.

Jest was the standard for React tests for years, with a slow start, cumbersome transformer configuration, and growing incompatibilities with ESM. Vitest shares Vite's configuration and transformer, starts in milliseconds, offers a Jest-compatible API, and integrates seamlessly into Vite-based React projects.

An upload test that only ever works with a tiny, few-kilobyte sample file actually checks only a fraction of the cases that genuinely matter, since the most common real-world problems only surface with large files near the upload limit, with deliberately or accidentally wrong file types, and with the actual content of a subsequently downloaded file. A robust test strategy for file uploads and downloads deliberately and automatically covers exactly these three areas.

The choice between OpenAPI-First and Code-First is not a technical decision, it is an organizational one. It depends on team size, product maturity, number of consumers and synchronization requirements. This guide provides a structured decision framework, with concrete tooling recommendations for both approaches.

Component Testing with Cypress closes the gap between isolated unit tests and slow end to end runs. Vue components are actually mounted in the browser, with a real DOM, real events, and controllable network calls, without booting up the entire application.

AI-generated code often looks convincingly finished, yet it frequently hides subtle edge-case bugs, outdated API calls, or overlooked security gaps that a reviewer without a targeted eye can easily wave through. This article covers typical failure patterns of AI assistants and provides a practical checklist that lets developers review AI-generated changes just as thoroughly as human-written code.

A single code change rarely worsens a product page's load time noticeably, but twenty such small, individually inconspicuous degradations over several months add up to an overall considerably slower application, without any single, clearly responsible commit being identifiable for it. A performance budget wired into the CI pipeline as an automated test assertion prevents exactly this creeping problem, by immediately checking every single change against fixed, objective thresholds, instead of monitoring performance only occasionally and manually.

If you only find out about quality gates in the CI pipeline, you lose minutes or hours on feedback loops that could have been resolved locally in seconds. PHPStan, PHPUnit, PHPCS and Rector can be integrated into PhpStorm so that errors become visible right at the moment you save, without ever leaving the command line.

Components that handle data fetching, form validation and UI state all at once are hard to test, hard to maintain and hard to reuse. Custom Hook Extraction is the fundamental React pattern that separates logic from presentation, making both better at the same time.

Without mocking, an unfinished backend endpoint blocks the entire frontend development effort. GraphQL mocking at the schema level makes frontend teams independent, enables testing of error scenarios, and significantly speeds up the development cycle.