--- title: "Vitest 3 is out: what changes for your Vue tests · vuejs.school" description: "Vitest 3.0 brings a rewritten reporter, inline workspaces and line-number filtering. Most Vue tests pass unchanged; a few spy and timer habits do not." canonical_url: "https://vuejs.school/community/blog/vitest-3-what-changes-for-vue-tests" meta: "og:description": "Vitest 3.0 brings a rewritten reporter, inline workspaces and line-number filtering. Most Vue tests pass unchanged; a few spy and timer habits do not." "og:image": "https://vuejs.school/_og/d/a_~Vml0ZXN0IDMgaXMgb3V0OiB3aGF0IGNoYW5nZXMgZm9yIHlvdXIgVnVlIHRlc3RzIMK3IHZ1ZWpzLnNjaG9vbA%2Cc_OgCard.takumi%2Ctitle_~Vml0ZXN0IDMgaXMgb3V0OiB3aGF0IGNoYW5nZXMgZm9yIHlvdXIgVnVlIHRlc3Rz%2Cdescription_~Vml0ZXN0IDMuMCBicmluZ3MgYSByZXdyaXR0ZW4gcmVwb3J0ZXIsIGlubGluZSB3b3Jrc3BhY2VzIGFuZCBsaW5lLW51bWJlciBmaWx0ZXJpbmcuIE1vc3QgVnVlIHRlc3RzIHBhc3MgdW5jaGFuZ2VkOyBhIGZldyBzcHkgYW5kIHRpbWVyIGhhYml0cyBkbyBub3Qu%2Ceyebrow_~UmVsZWFzZSBub3RlcyDCtyA2IG1pbiByZWFk%2Ctint_mint%2Cp_Ii9jb21tdW5pdHkvYmxvZy92aXRlc3QtMy13aGF0LWNoYW5nZXMtZm9yLXZ1ZS10ZXN0cyI%2Cs_mYKym78roAHz-wRr.png" "og:image:alt": "Vitest 3 is out: what changes for your Vue tests · vuejs.school" "og:image:height": "600" "og:image:type": image/png "og:image:width": "1200" "og:title": "Vitest 3 is out: what changes for your Vue tests · vuejs.school" "twitter:image": "https://vuejs.school/_og/d/a_~Vml0ZXN0IDMgaXMgb3V0OiB3aGF0IGNoYW5nZXMgZm9yIHlvdXIgVnVlIHRlc3RzIMK3IHZ1ZWpzLnNjaG9vbA%2Cc_OgCard.takumi%2Ctitle_~Vml0ZXN0IDMgaXMgb3V0OiB3aGF0IGNoYW5nZXMgZm9yIHlvdXIgVnVlIHRlc3Rz%2Cdescription_~Vml0ZXN0IDMuMCBicmluZ3MgYSByZXdyaXR0ZW4gcmVwb3J0ZXIsIGlubGluZSB3b3Jrc3BhY2VzIGFuZCBsaW5lLW51bWJlciBmaWx0ZXJpbmcuIE1vc3QgVnVlIHRlc3RzIHBhc3MgdW5jaGFuZ2VkOyBhIGZldyBzcHkgYW5kIHRpbWVyIGhhYml0cyBkbyBub3Qu%2Ceyebrow_~UmVsZWFzZSBub3RlcyDCtyA2IG1pbiByZWFk%2Ctint_mint%2Cp_Ii9jb21tdW5pdHkvYmxvZy92aXRlc3QtMy13aGF0LWNoYW5nZXMtZm9yLXZ1ZS10ZXN0cyI%2Cs_mYKym78roAHz-wRr.png" "twitter:image:alt": "Vitest 3 is out: what changes for your Vue tests · vuejs.school" --- > Index of every page on this site: [llms.txt](https://vuejs.school/llms.txt) ## What shipped The announcement names five headline changes: - The terminal reporter was rewritten. Output flickers less and stays stable while tests run. The reporter API behind the `reporters` option was redesigned with a simpler lifecycle: the old `onTaskUpdate` hook still works but is deprecated in favour of hooks such as `onTestCaseResult`. - Workspaces can be declared inline. A monorepo lists its projects straight in the config file with `workspace: ['packages/*']`, with no separate workspace file. - Browser mode gets `browser.instances`, an array that runs the same tests in several browsers from one config and one Vite server. - You can run a single test by its line number: `vitest src/Counter.spec.ts:12`. - The `vitest/node` API was redesigned and documented, and the team plans to drop its experimental label in the next minor. The [changelog](https://github.com/vitest-dev/vitest/releases/tag/v3.0.0) adds smaller features: the new matchers `toBeOneOf` and `toHaveBeenCalledExactlyOnceWith`, `expect.toSatisfy()` as an asymmetric matcher, a `describe.for` that mirrors `test.for`, and a `summary` option for the default reporter. ## Breaking changes that can fail a component test The announcement calls the breaking changes small, and for a typical Vue project that is true. The migration guide linked from the announcement lists them in full. These four can reach a component test. **`mockReset()` now restores the original implementation.** Before, `mockReset()` turned a mock into an empty function that returns `undefined`. Now a mock created with `vi.fn(() => 'hello')` goes back to returning `'hello'` after a reset. If your `afterEach` relied on a reset to silence a mock, the mock now keeps its behaviour. **`vi.spyOn()` reuses an existing spy.** Spying on a method that is already spied on returns the same spy instead of wrapping it again, so `mockRestore()` restores the real method rather than the previous spy. This fixes a class of leaky tests, but a test that counted on two separate spies will see one. **Fake timers fake more by default.** `vi.useFakeTimers()` used to replace a fixed list: `setTimeout`, `clearTimeout`, `setInterval`, `clearInterval`, `setImmediate`, `clearImmediate` and `Date`. Now it replaces every timer-related API it finds except `process.nextTick`. That includes `performance.now()` and, in a DOM environment such as happy-dom or jsdom, `requestAnimationFrame`. A component that measures elapsed time with `performance.now()` will see time stand still until you advance it. To get the old list back for every test, set it in your config: *vitest.config.ts* ``` import { defineConfig } from 'vitest/config' export default defineConfig({ test: { fakeTimers: { toFake: ['setTimeout', 'clearTimeout', 'setInterval', 'clearInterval', 'setImmediate', 'clearImmediate', 'Date'], }, }, }) ``` `toFake` names exactly what gets faked. To change one test only, pass the same option to that call instead: `vi.useFakeTimers({ toFake: ['setTimeout', 'clearTimeout'] })`. **Error equality is stricter.** `toEqual` and `toThrowError` now compare an error's `name`, `message` and `cause`, and check the prototype. `expect(fn).toThrowError(new Error('Bad input'))` fails when the thrown error is a `TypeError`, where before it passed. Match the class you actually throw. Two smaller changes do not fail a test: - Passing options as the third argument, `it('saves', async () => {}, { timeout: 10_000 })`, is deprecated. Put the object second: `it('saves', { timeout: 10_000 }, async () => {})`. A plain number as the third argument still works. The next major version will turn the warning into an error, so move the options now. - Test files are always excluded from the coverage report, even if you overrode `coverage.exclude`. If your coverage number moves a little, that is why. ## Fix a test that relied on mockReset `ShoppingList` takes a `load` function as a prop, calls it once, and lists what it returns. When `load` returns nothing, it shows an empty state. *src/components/ShoppingList.vue* ``` ``` Its test file resets the mock after each test. It passed on Vitest 2 and fails on Vitest 3: *src/components/\_\_tests\_\_/ShoppingList.spec.ts**Breaks*** ``` import { mount } from '@vue/test-utils' import { afterEach, expect, it, vi } from 'vitest' import ShoppingList from '../ShoppingList.vue' const load = vi.fn(() => ['Milk', 'Eggs']) afterEach(() => { load.mockReset() }) it('renders the items', () => { const wrapper = mount(ShoppingList, { props: { load } }) expect(wrapper.text()).toContain('Milk') }) it('shows the empty state', () => { const wrapper = mount(ShoppingList, { props: { load } }) expect(wrapper.text()).toContain('Nothing to buy') }) ``` The second test never said what `load` should return. It leaned on `mockReset()` having turned `load` into a function that returns `undefined`, which the component turns into an empty list. On Vitest 3 the reset restores the `['Milk', 'Eggs']` implementation, the list renders, and the assertion fails with `expected 'MilkEggs' to contain 'Nothing to buy'`. The fix is to say what you mean. Replace the second test with one that sets its own return value: *src/components/\_\_tests\_\_/ShoppingList.spec.ts**Works*** ``` it('shows the empty state', () => { load.mockReturnValue([]) const wrapper = mount(ShoppingList, { props: { load } }) expect(wrapper.text()).toContain('Nothing to buy') }) ``` That version passes on both majors, and it reads better: the test states its own setup instead of inheriting it from a hook. Search your suites for `mockReset` and for `vi.fn(` with an implementation, and check each pair for the same hidden dependency. ## What stays the same Most of what a Vue component test touches is unchanged: - Vue Test Utils. Version 2.4 is the current release, and `mount`, `shallowMount`, `wrapper.find`, `trigger` and `emitted` behave as before. The library does not depend on the test runner at all. - The `environment: 'happy-dom'` or `'jsdom'` setting. - The `vitest.config.ts` that create-vue generates, with `mergeConfig(viteConfig, ...)`. It needs no edit. - Snapshots. `toMatchSnapshot` works exactly as it did. The change is in the API of the `@vitest/snapshot` package, which now supports several snapshot states in one run and matters only to code that calls it directly. ## How to upgrade First, the one check: confirm your Vite version with `npx vite --version`. If it prints 5.x or 6.x you are ready. If it prints 4.x, upgrade Vite before touching Vitest, because Vitest 3 depends on Vite 5 or 6. Then make sure your suite is green on Vitest 2, so every failure after the upgrade is the upgrade's doing: ``` npx vitest --run ``` Now install Vitest and its companion packages in one command. The coverage, UI and browser packages each expect the exact same version as `vitest`, so upgrade them together: ``` npm install -D vitest@3 @vitest/coverage-v8@3 ``` Add `@vitest/ui@3` or `@vitest/browser@3` to that line if you use them. Run the suite again, and read the warnings before the failures: the third-argument deprecation prints one warning for each test or `describe` that still passes its options last. ## Upgrade now or wait Upgrade now if your project is on Vite 5 or 6 and your suite is green. The breaking changes are findable by search, the new reporter is easier to read, and running one test by line number is a small thing you will use often. An app already on Vite 6 gains the most, because Vitest 3 can use the app's own Vite instead of a separate Vite 5. Wait if you are on Vite 4, and upgrade Vite first. Fake timers are not a reason to wait. If you are unsure what your timer tests depend on, add the `toFake` list above when you upgrade, get the suite green, and remove the list later, one timer test at a time. **Check it stuck**3 questions from the Vitest and Vue Test Utils quiz. [**Practice now**](https://vuejs.school/learn/testing/vitest-and-vue-test-utils?tab=quiz) **Was this helpful?** ## **Keep reading** [Release notes · 6 min read**Vitest 5: what changed for Vue tests**](https://vuejs.school/community/blog/vitest-5-what-changed-for-vue-tests) [Release notes · 6 min read**Vitest 5 release candidate: what's coming for Vue tests**](https://vuejs.school/community/blog/vitest-5-rc-whats-coming) ```json {"@context":"https://schema.org","@graph":[{"@id":"https://vuejs.school/#website","@type":"WebSite","description":"A free AI-instructed school for Vue.js. 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