Catch TypeScript Type Errors in Vitest Before CI Fails
Use Vitest typecheck to run tsc over test and source files, catching type errors runtime tests miss.
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typescriptPartial Mocking in Vitest: Replace Only What You Need with vi.importActual
Use Vitest's vi.mock with vi.importActual to partially mock a module — keep real helpers, replace only the heavy or external functions. Includes a worked TypeScript example, hoisting explanation, and common pitfalls.
Replace Fixed Test Delays with Vitest expect.poll
Fixed-delay sleeps make async tests either flaky or slow. Vitest's expect.poll retries standard matchers until a condition passes, giving you a deterministic middle ground—if you tune it correctly.
Diagnosing and Fixing Snapshot Failures in Vitest
When a Vitest snapshot test fails, the culprit is almost always a mis‑matched output. This guide walks through the most common causes, a quick diagnostic table, step‑by‑step checks, and the right fixes so you can keep your snapshots trustworthy.
Choosing the Right Vitest Environment: Node, JSDOM, or Happy-DOM
Learn how to choose between Node, JSDOM, and Happy-DOM in Vitest to balance test execution speed with browser API fidelity.
Reduce Test Duplication with Vitest’s test.each
Learn how Vitest’s test.each lets you drive many test cases from a single table, reducing copy‑pasted blocks while keeping clear titles and TypeScript‑inferred parameters.
Solving Environment Clash with Vitest Workspaces
Stop fighting with environment comments. Learn how to use Vitest Workspaces to run Node and JSDOM tests concurrently in a single project without configuration leakage.
Testing Private Helpers Without Exporting Them
Keep private utilities private and still test them with Vitest in-source testing, then verify Vite strips the tests from production builds.
Snapshot Testing in Vitest: How to Capture, Update, and Verify Stable Output
Learn how Vitest’s built‑in snapshot testing captures output, updates snapshots with –u, and avoids pitfalls like dynamic data and snapshot bloat.
nodejs