- How to Trigger React Error Boundary (Dev and Test)· 4 min read
Trigger a React error boundary by throwing during render, testing the fallback in Jest, and using showBoundary for async or event-handler errors.
- Mock IntersectionObserver in Jest Setup· 4 min read
Fix `IntersectionObserver is not defined` in Jest by adding a clean global mock in `jest.setup.ts`. Includes TypeScript-safe setup and a test example.
- Fix Jest "window.matchMedia is not a function"· 3 min read
jsdom in Jest has no window.matchMedia, so components that call it throw a TypeError. Add a matchMedia mock to your Jest setup file.
- Fixing Jest Error: 'Not Implemented window.scrollTo'· 1 min read
Fix the Jest jsdom error "Not implemented: window.scrollTo" by mocking window.scrollTo in your setup file. Includes a test to confirm that the mock works.
- How to Solve the "ResizeObserver is Not Defined" Error in Jest Tests· 2 min read
Fix "ResizeObserver is not defined" in Jest by mocking ResizeObserver in your setup file, so tests for components that use it run in jsdom.
- Testing Next.js Image Component· 3 min read
Simple way to test Next.js Image in Jest by mocking it as a plain img tag, plus checks and common mistakes.
- Testing the next-i18next Library with Jest· 2 min read
Simple way to test next-i18next in Jest by mocking translation hooks so component tests stay focused and stable.
- How to Resolve 'Cannot use import statement outside a module' Error when Mocking Swiper JS with Jest· 2 min read
Fix Jest "Cannot use import statement outside a module" when mocking Swiper by adjusting transformIgnorePatterns.
- Resolving Jest Error with EMFILE Too Many Open Files· 2 min read
Fix the Jest EMFILE too many open files error by lowering maxWorkers, ignoring build folders, raising ulimit, and running in band on CI.