10 articles
RSSHow to fix Jest setup file issues — setupFilesAfterFramework vs setupFiles, global mocks not applying, @testing-library/jest-dom matchers, module mocking in setup, and TypeScript setup files.
How to fix Jest async test timeouts — missing await, unresolved Promises, done callback misuse, global timeout configuration, fake timers, and async setup/teardown issues.
How to fix Jest coverage not collecting all files — collectCoverageFrom config, coverage thresholds, Istanbul ignore comments, ts-jest setup, and Babel transform issues.
How to fix Jest fake timers not working — useFakeTimers setup, runAllTimers vs advanceTimersByTime, async timers, React testing with act(), and common timer test mistakes.
How to fix Jest module mocks not working — hoisting behavior, ES module mocks, factory functions, mockReturnValue vs implementation, and clearing mocks between tests.
How to fix Jest failing with 'Cannot use import statement outside a module' — configuring Babel transforms, using experimental VM modules, migrating to Vitest, and handling ESM-only packages.
How to fix Jest snapshot failures — updating outdated snapshots, removing obsolete ones, fixing inline snapshots, preventing brittle snapshot tests, and managing snapshots in CI.
How to fix jest.mock() not intercepting module calls — why mocks are ignored, how to correctly mock ES modules, default exports, named exports, and fix hoisting issues in Jest tests.
How to fix Jest 'Exceeded timeout of 5000ms for a test' errors caused by unresolved promises, missing done callbacks, async/await mistakes, and slow database or network calls in tests.
How to fix the Jest 'Cannot find module' error by configuring moduleNameMapper, moduleDirectories, tsconfig paths, and resolving ESM, monorepo, and dependency issues.