chore: migrate test runner from Jest to Vitest by FabienMotte · Pull Request #6937 · algolia/instantsearch

FabienMotte · 2026-03-20T17:12:30Z

Summary

Migrate the entire monorepo test runner from Jest 27 to Vitest 4. This eliminates the Babel dependency for tests, leverages Vite's native ESM/TypeScript/JSX handling, and modernizes the test infrastructure.

Core migration

Replace jest.config.js with vitest.config.ts at root level and in subpackages (algoliasearch-helper, create-instantsearch-app)
Mechanical jest.* → vi.* replacements across all test files (~1400+ vi.fn(), vi.mock(), vi.spyOn(), etc.)
Migrate jest.requireActual() (sync) → await vi.importActual() (async) in all mock factories
Replace @jest-environment pragmas with @vitest-environment across ~200 test files
Migrate custom matchers (toWarnDev, toMatchNormalizedInlineSnapshot, Vue matchers) to Vitest types and APIs
Convert done() callback patterns to return new Promise() wrapper (deprecated in Vitest)
Replace jest-environment-jsdom custom environment with Vitest's built-in jsdom (Node 20 provides all needed globals natively)

Subpackage migrations

algoliasearch-helper: Rewrite test/run.js to use startVitest() API instead of jest.runCLI()
create-instantsearch-app: Convert entire source from CJS to ESM ("type": "module"), add dual exports (index.js + index.cjs) for backwards compatibility, rename template configs from .template.js → .template.cjs, add .template.js fallback for custom templates

Configuration updates

TypeScript: Add "types": ["vitest/globals"], remove @types/jest
ESLint: Replace eslint-plugin-jest with eslint-plugin-vitest, update all rule references
Babel: Remove Jest/CJS code path, keep Storybook branch only
CI: Update .circleci/config.yml for Vitest commands and JUnit output paths
Vue: Support both Vue 2 (@vitejs/plugin-vue2) and Vue 3 (@vitejs/plugin-vue) via env var switching

Performance optimizations

happy-dom: Switch test environment from jsdom to happy-dom across ~200 test files for faster DOM simulation
Threads: Switch Vitest to threads pool in CI and test runners for better parallelism

Vitest 4 compatibility fixes

Fix Mock type params, implicit any, and spread arg errors for Vitest 4
Import Mock, MockInstance, MockedFunction types from vitest instead of relying on globals
Drop vi.fn() type args (removed in Vitest 4), remove unused imports
Remove leftover Jasmine type reference that polluted vitest globals
Add vite@8 to root devDependencies for correct type resolution

Vue 3 fixes

Resolve Vue 3 dependencies in Vitest config
Repair Vue 3 Vitest prep script and snapshots
Remove redundant esbuild config from Vitest

Codemod test migration

Migrate jscodeshift codemod tests (instantsearch-codemods, instantsearch.js/scripts/transforms) to Vitest
Replace jscodeshift/dist/testUtils.defineTest (which uses CJS require() for transforms) with applyTransform + ESM imports
Remove codemod/transform exclusions from vitest.config.ts so all tests run in the main suite

Bug fixes along the way

Fix unhandled errors/rejections across the test suite (mock routers missing dispose(), incorrect Promise constructors, etc.)
Normalize widget snapshots before inline assertions
Remove stale dependencies (jsdom-global, babel-eslint)
Handle jsdom v29 behavioral changes (accessible name computation, non-configurable sessionStorage)
Disable OXC JSX dev mode to prevent __self/__source attributes breaking snapshots and accessible name assertions

Cleanup

Remove all Jest config files, custom Jest environments, and Jest-specific dependencies
Remove obsolete common widget snapshots
Rename remaining "jest" references to "vitest" in comments and file paths
Regenerate all snapshots

Benchmarks

Local

Local benchmarks on Apple Silicon via yarn test (wall-clock time, no coverage).

	Jest 27 (`master`)	Vitest 4 (this branch)
Test files	377	377
Tests	4,311 (173 skipped)	4,311 (173 skipped)
Wall-clock time	129.54s	137.18s

Vitest wall-clock time is higher locally due to Vite's module transformation and environment setup overhead. The tradeoff is eliminating the Babel transpilation pipeline, gaining native ESM/TypeScript/JSX support, and modernizing the DX (HMR watch mode, better error formatting, native coverage via v8).

CircleCI

Recent CircleCI unit tests job runs on this branch are more stable and faster on rolling metrics than master.

	Jest 27 (`master`)	Vitest 4 (this branch)
Latest run	4m 18.9s	4m 39.7s
Median of last 5 runs	4m 57.0s	4m 39.7s
Average of last 5 runs	5m 26.4s	4m 39.7s
Last 5 range	4m 15.3s to 7m 49.7s	4m 28.4s to 4m 47.9s

The latest single run is noisy, but the last-5 median is about 17s faster on this branch and the last-5 average is about 47s faster (-14.3%). Some longer master runs are likely inflated by flaky tests being retried, which makes the branch's tighter timing range a better signal than any one-off run.

Test plan

Root vitest suite passes (377 test files, 4,138 tests)
algoliasearch-helper tests pass (95 test files, 445 tests)
create-instantsearch-app tests pass (10 test files, 74 tests)
yarn lint passes
TypeScript compilation passes with vitest/globals types
CI pipeline validates all test jobs (unit tests, Vue v3 tests, JUnit output)

…om templates

pkg-pr-new · 2026-03-20T18:01:19Z

More templates

algoliasearch-helper

npm i https://pkg.pr.new/algolia/instantsearch/algoliasearch-helper@6937

instantsearch-ui-components

npm i https://pkg.pr.new/algolia/instantsearch/instantsearch-ui-components@6937

instantsearch.css

npm i https://pkg.pr.new/algolia/instantsearch/instantsearch.css@6937

instantsearch.js

npm i https://pkg.pr.new/algolia/instantsearch/instantsearch.js@6937

react-instantsearch

npm i https://pkg.pr.new/algolia/instantsearch/react-instantsearch@6937

react-instantsearch-core

npm i https://pkg.pr.new/algolia/instantsearch/react-instantsearch-core@6937

react-instantsearch-nextjs

npm i https://pkg.pr.new/algolia/instantsearch/react-instantsearch-nextjs@6937

react-instantsearch-router-nextjs

npm i https://pkg.pr.new/algolia/instantsearch/react-instantsearch-router-nextjs@6937

vue-instantsearch

npm i https://pkg.pr.new/algolia/instantsearch/vue-instantsearch@6937

commit: c44ceb6

…st globals

…MatchNormalizedSnapshot

…orts

…rg errors

The `execSync` call in the install test takes longer than Vitest's default 5000ms timeout.

Replace jscodeshift's `defineTest` (which uses CJS `require()` to load .ts transforms) with `applyTransform` + ESM imports. Remove codemod and transform exclusions from vitest.config.ts so all tests run in the main suite.

Haroenv · 2026-04-14T11:24:54Z

what was missing to finish this @FabienMotte? seems like the CI was green before rebase

FabienMotte · 2026-04-14T11:27:23Z

what was missing to finish this @FabienMotte? seems like the CI was green before rebase

Just missing some reviews, I'll mark it as ready and solve the conflicts

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Haroenv · 2026-04-14T11:56:35Z

I also see the timing is almost exactly the same. Is that something that can be fixed? otherwise I'm not sure if there's much value?

FabienMotte · 2026-04-23T14:08:15Z

I also see the timing is almost exactly the same. Is that something that can be fixed? otherwise I'm not sure if there's much value?

I agree, I tried multiple solutions to reduce the test's duration, but ultimately, it still takes more time.

Should we close it for now and revisit it later?

Haroenv · 2026-04-24T11:54:41Z

yes, let's stay with jest for now then. Thanks for the exploration though!

FabienMotte added 9 commits March 21, 2026 02:21

chore: migrate test runner from Jest to Vitest

56e6067

chore(create-instantsearch-app): convert source from CJS to ESM

8db375c

chore: remove leftover Jest config and unused vitest environment

f76fe0c

chore: rename jest references to vitest in comments and paths

609419f

chore: remove stale dependencies (jsdom-global, babel-eslint)

cdd3dbc

chore: fix unhandled errors in test suite

7894531

fix(create-instantsearch-app): preserve CJS require() compatibility

3633440

fix(create-instantsearch-app): support .template.js fallback for cust…

0cceac9

…om templates

fix(create-instantsearch-app): rename release-templates script to .cjs

71ed792

FabienMotte force-pushed the chore/jest-to-vitest-migration branch from fce176c to 71ed792 Compare March 20, 2026 17:24

test: fix declaration builds for __DEV__ globals

c42c060

FabienMotte added 18 commits March 21, 2026 03:05

chore: update Vitest CI worker flags

38d4f15

fix: resolve lint issues from Vitest migration

05284c4

fix(types): remove leftover Jasmine type reference that polluted vite…

c7892ee

…st globals

fix(tests): restore toMatchNormalizedInlineSnapshot, remove unused to…

b7ef473

…MatchNormalizedSnapshot

fix(tests): drop vi.fn() type args for vitest 4 and remove unused imp…

dfde5d9

…orts

fix(tests): import Mock, MockInstance, MockedFunction types from vitest

7322523

fix(tests): fix vitest 4 Mock type params, implicit any, and spread a…

7678b2b

…rg errors

chore: add vite 8 to root devDependencies for correct type resolution

9320e4c

fix(tests): fix import order in insights-client-test

5ad5860

fix: normalize widget snapshots before inline assertions

f7a0cd1

fix: update CircleCI Vitest command for Vue v3 tests

5dc1397

chore: switch Vitest to threads in CI and test runners

8b64ff6

test: remove obsolete common widget snapshots

f83d367

fix: remove redundant esbuild config from Vitest

1cd57d6

fix: resolve Vue 3 dependencies in Vitest config

3733afe

fix: repair Vue 3 Vitest prep and snapshots

22808e4

perf: switch test environment from jsdom to happy-dom

4608e89

fix: increase test timeout for create-instantsearch-app e2e tests

5fd4f8d

The `execSync` call in the install test takes longer than Vitest's default 5000ms timeout.

FabienMotte added 3 commits March 22, 2026 18:26

test: migrate jscodeshift codemod tests to Vitest

06a2051

Replace jscodeshift's `defineTest` (which uses CJS `require()` to load .ts transforms) with `applyTransform` + ESM imports. Remove codemod and transform exclusions from vitest.config.ts so all tests run in the main suite.

fix: correct import order in transforms test

83804b3

fix(types): resolve type errors in codemod tests

c44ceb6

FabienMotte marked this pull request as ready for review April 14, 2026 11:28

Copilot AI review requested due to automatic review settings April 14, 2026 11:28

Copilot AI reviewed Apr 14, 2026

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Haroenv closed this Apr 24, 2026

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chore: migrate test runner from Jest to Vitest#6937

chore: migrate test runner from Jest to Vitest#6937
FabienMotte wants to merge 31 commits intomasterfrom
chore/jest-to-vitest-migration

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Summary

Core migration

Subpackage migrations

Configuration updates

Performance optimizations

Vitest 4 compatibility fixes

Vue 3 fixes

Codemod test migration

Bug fixes along the way

Cleanup

Benchmarks

Local

CircleCI

Test plan

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FabienMotte commented Mar 20, 2026 •

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