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fix(jest-config): correct maxWorkers description - #16466

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januththedev:fix-maxworkers-description
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fix(jest-config): correct maxWorkers description#16466
januththedev wants to merge 2 commits into
jestjs:mainfrom
januththedev:fix-maxworkers-description

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@januththedev januththedev commented Sep 26, 2026

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Fixes #16465. The scaffolded maxWorkers description now matches the implemented floor-and-clamp percentage formula, with a regression assertion and changelog entry. Local dependency installation was not completed, so the focused test will run in CI.

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  • ✅ login: januththedev / name: Januth Nimnal (2a4895a)

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@github-actions github-actions Bot added the require-changelog If a PR does requires a changelog entry label Sep 26, 2026
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babel-jest

npm i https://pkg.pr.new/babel-jest@16466

babel-plugin-jest-hoist

npm i https://pkg.pr.new/babel-plugin-jest-hoist@16466

babel-preset-jest

npm i https://pkg.pr.new/babel-preset-jest@16466

create-jest

npm i https://pkg.pr.new/create-jest@16466

@jest/diff-sequences

npm i https://pkg.pr.new/@jest/diff-sequences@16466

expect

npm i https://pkg.pr.new/expect@16466

@jest/expect-utils

npm i https://pkg.pr.new/@jest/expect-utils@16466

jest

npm i https://pkg.pr.new/jest@16466

jest-changed-files

npm i https://pkg.pr.new/jest-changed-files@16466

jest-circus

npm i https://pkg.pr.new/jest-circus@16466

jest-cli

npm i https://pkg.pr.new/jest-cli@16466

jest-config

npm i https://pkg.pr.new/jest-config@16466

@jest/console

npm i https://pkg.pr.new/@jest/console@16466

@jest/core

npm i https://pkg.pr.new/@jest/core@16466

@jest/create-cache-key-function

npm i https://pkg.pr.new/@jest/create-cache-key-function@16466

jest-diff

npm i https://pkg.pr.new/jest-diff@16466

jest-docblock

npm i https://pkg.pr.new/jest-docblock@16466

jest-each

npm i https://pkg.pr.new/jest-each@16466

@jest/environment

npm i https://pkg.pr.new/@jest/environment@16466

jest-environment-jsdom

npm i https://pkg.pr.new/jest-environment-jsdom@16466

@jest/environment-jsdom-abstract

npm i https://pkg.pr.new/@jest/environment-jsdom-abstract@16466

jest-environment-node

npm i https://pkg.pr.new/jest-environment-node@16466

@jest/expect

npm i https://pkg.pr.new/@jest/expect@16466

@jest/fake-timers

npm i https://pkg.pr.new/@jest/fake-timers@16466

@jest/get-type

npm i https://pkg.pr.new/@jest/get-type@16466

@jest/globals

npm i https://pkg.pr.new/@jest/globals@16466

jest-haste-map

npm i https://pkg.pr.new/jest-haste-map@16466

jest-jasmine2

npm i https://pkg.pr.new/jest-jasmine2@16466

jest-leak-detector

npm i https://pkg.pr.new/jest-leak-detector@16466

jest-matcher-utils

npm i https://pkg.pr.new/jest-matcher-utils@16466

jest-message-util

npm i https://pkg.pr.new/jest-message-util@16466

jest-mock

npm i https://pkg.pr.new/jest-mock@16466

@jest/pattern

npm i https://pkg.pr.new/@jest/pattern@16466

jest-phabricator

npm i https://pkg.pr.new/jest-phabricator@16466

jest-regex-util

npm i https://pkg.pr.new/jest-regex-util@16466

@jest/reporters

npm i https://pkg.pr.new/@jest/reporters@16466

jest-resolve

npm i https://pkg.pr.new/jest-resolve@16466

jest-resolve-dependencies

npm i https://pkg.pr.new/jest-resolve-dependencies@16466

jest-runner

npm i https://pkg.pr.new/jest-runner@16466

jest-runtime

npm i https://pkg.pr.new/jest-runtime@16466

@jest/schemas

npm i https://pkg.pr.new/@jest/schemas@16466

jest-snapshot

npm i https://pkg.pr.new/jest-snapshot@16466

@jest/snapshot-utils

npm i https://pkg.pr.new/@jest/snapshot-utils@16466

@jest/source-map

npm i https://pkg.pr.new/@jest/source-map@16466

@jest/test-result

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@jest/test-sequencer

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@jest/transform

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@jest/types

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jest-util

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jest-validate

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jest-watcher

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jest-worker

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pretty-format

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commit: 5392a6e

@januththedev
januththedev force-pushed the fix-maxworkers-description branch from 9916d27 to 19498ac Compare September 26, 2026 12:55
@januththedev
januththedev force-pushed the fix-maxworkers-description branch from 19498ac to 218338e Compare September 26, 2026 13:35
@januththedev

januththedev commented Sep 26, 2026

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The first CI run failed three create-jest snapshot tests, and that one was on me:

● init › ... › should return the default configuration (an empty config)
● init › ... › should generate empty config with mjs extension
● init › project using jest.config.ts › ask the user whether he wants to use Typescript or not

create-jest init embeds the Descriptions text as comments in the config it writes, so changing a description changes the generated file. The committed snapshot in packages/create-jest/src/__tests__/__snapshots__/init.test.ts.snap still carried the old maxWorkers wording, so the three snapshots that include it no longer matched:

- // ... E.g. maxWorkers: 10% will use 10% of your CPU amount + 1 as the maximum worker number. ...
+ // ... E.g. maxWorkers: 10% will use 10% of the available CPUs, rounded down with a minimum of 1. ...

I updated those three snapshot entries to match. A repo-wide grep confirmed init.test.ts.snap is the only file carrying that string, so there is no other stale copy.

Note for review: the old wording was not merely imprecise. getMaxWorkers computes Math.max(Math.floor(numCpus * percentage / 100), 1), so 10% floors the CPU count and then clamps to a minimum of 1 — it never adds 1.

I could not execute the Jest suite locally to confirm the snapshot regeneration, since this checkout has no node_modules and a full monorepo install was not practical here. Instead I verified programmatically that all three snapshot lines are byte-identical to the maxWorkers string in Descriptions.ts, which is exactly the transformation the failing assertion reported.

@januththedev

januththedev commented Sep 26, 2026

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CI is green on 218338e. All test jobs pass on Ubuntu, Windows, and macOS across Node 18 through 26 plus the jasmine2 runs, along with the leak-detection, coverage, and TypeScript compatibility jobs. The three create-jest snapshot tests that failed before now pass with the updated snapshot.

The only check still red is EasyCLA, which needs the CLA signature from a human account rather than anything in the diff.

@januththedev
januththedev force-pushed the fix-maxworkers-description branch from 218338e to 2a4895a Compare October 3, 2026 10:41
@cherenkov cherenkov mentioned this pull request Oct 12, 2026
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maxWorkers description uses the wrong percentage formula

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