feat: support test sharding by 9aoy · Pull Request #921 · web-infra-dev/rstest

9aoy · 2026-01-29T09:47:03Z

Summary

Support shard test files for parallel execution. This is particularly useful for parallelizing tests in CI/CD environments, allowing you to split the test suite into multiple parts and run them independently across different jobs, thereby reducing overall test time.

Usage

npx rstest --shard 1/3

import { defineConfig } from '@rstest/core';

export default defineConfig({
  shard: {
    count: 3,
    index: 1,
  },
});

Checklist

Tests updated (or not required).
Documentation updated (or not required).

gemini-code-assist · 2026-01-29T09:47:31Z

Summary of Changes

Hello @9aoy, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant new feature: test sharding. It enables users to distribute their test files across multiple parallel processes, which is particularly advantageous for accelerating test execution in continuous integration and continuous deployment (CI/CD) pipelines. The implementation provides flexible configuration through both command-line arguments and the rstest.config.ts file, ensuring broad applicability and ease of use.

Highlights

Test Sharding Feature: Introduced the ability to shard test files for parallel execution, primarily designed to accelerate test runs in CI/CD environments.
Flexible Configuration: Supports configuring test sharding via both a new CLI option (--shard <index>/<count>) and through the rstest.config.ts file (shard: { count: number, index: number }).
Cross-Environment Support: The sharding logic is seamlessly integrated and applied to both Node.js and browser-based test projects.
Robust Validation and Constraints: Includes comprehensive validation for shard parameters and prevents the use of sharding in watch mode or when configured on a per-project basis, enforcing it as a global setting.
New End-to-End Tests: Dedicated end-to-end tests have been added to thoroughly verify the correct behavior and functionality of the test sharding feature.
Comprehensive Documentation: New documentation pages for the shard option have been added in both English and Chinese, detailing its usage, configuration, and important considerations.

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gemini-code-assist

Code Review

This pull request introduces test sharding, a significant feature for parallelizing test execution in CI/CD environments. The implementation is comprehensive, covering CLI options, configuration, core sharding logic for both Node and Browser environments, and robust validation. New e2e tests ensure the feature works as expected, and documentation has been added to guide users. The code is well-structured, though the sharding logic in runTests.ts adds some complexity. My review includes one suggestion for improving type safety and code clarity when passing sharded entries to the browser test runner. Overall, this is a solid contribution.

gemini-code-assist · 2026-01-29T09:49:00Z

packages/core/src/core/runTests.ts

+    const browserEntries = new Map();
+    if (shard) {
+      for (const p of browserProjectsToRun) {
+        browserEntries.set(
+          p.environmentName,
+          entriesCache.get(p.environmentName),
+        );
+      }
+    }


The shardedEntries option on runBrowserModeTests expects a Map<string, { entries: Record<string, string> }>. Currently, you are passing the entire value from entriesCache, which may include an extra fileFilters property. While this works due to structural typing, it's cleaner and more type-safe to construct an object that precisely matches the expected type. This improves code clarity and maintainability by ensuring only the necessary data is passed.

Suggested change

const browserEntries = new Map();

if (shard) {

for (const p of browserProjectsToRun) {

browserEntries.set(

p.environmentName,

entriesCache.get(p.environmentName),

);

}

}

const browserEntries = new Map<

string,

{ entries: Record<string, string> }

>();

if (shard) {

for (const p of browserProjectsToRun) {

// The filter for `browserProjectsToRun` ensures that `entriesCache.get(p.environmentName)`

// and its `entries` property are defined.

browserEntries.set(p.environmentName, {

entries: entriesCache.get(p.environmentName)!.entries,

});

}

}

…shard

cloudflare-workers-and-pages · 2026-01-30T04:09:23Z

Deploying rstest with Cloudflare Pages

Latest commit:	`c6346ab`
Status:	✅ Deploy successful!
Preview URL:	https://038d32ea.rstest.pages.dev
Branch Preview URL:	https://shard.rstest.pages.dev

View logs

Copilot

Pull request overview

This PR implements test sharding functionality to enable parallel test execution across multiple machines or CI/CD jobs, similar to Jest's --shard option. The feature allows users to split test files into multiple shards and run them independently to reduce overall test time.

Changes:

Added shard configuration option with CLI support via --shard <index>/<count>
Implemented sharding logic that distributes test files evenly across shards with consistent sorting
Integrated sharding support for both node and browser mode tests
Added comprehensive documentation in English and Chinese
Included validation to prevent shard usage in watch mode and at project level

Reviewed changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/core/src/utils/shard.ts	Core sharding logic for distributing test files and resolving sharded entries
packages/core/src/cli/init.ts	CLI argument parsing and validation for the --shard option
packages/core/src/cli/commands.ts	Added --shard CLI option definition
packages/core/src/core/runTests.ts	Integration of sharding into the main test runner for both node and browser modes
packages/core/src/core/rstest.ts	Validation to prevent shard in watch mode and per-project configuration
packages/core/src/core/listTests.ts	Integration of sharding into the list command
packages/core/src/core/browserLoader.ts	Updated browser module interface to support sharded entries
packages/browser/src/hostController.ts	Browser mode integration for sharded test execution
packages/core/src/types/config.ts	Type definitions for the shard configuration option
packages/core/src/types/core.ts	Added ProjectEntries type for sharded entry caching
packages/core/src/types/browser.ts	Added shardedEntries option to BrowserTestRunOptions
website/docs/en/config/test/shard.mdx	English documentation for the shard feature
website/docs/zh/config/test/shard.mdx	Chinese documentation for the shard feature
website/docs/en/config/test/projects.mdx	Updated ProjectConfig type to exclude shard
website/docs/zh/config/test/projects.mdx	Updated ProjectConfig type to exclude shard
website/docs/en/config/test/_meta.json	Added shard to documentation navigation
website/docs/zh/config/test/_meta.json	Added shard to documentation navigation
e2e/projects/shard.test.ts	Comprehensive e2e tests for sharding functionality
e2e/projects/index.test.ts	Updated error handling tests to use new helper methods
e2e/list/index.test.ts	Added test for list command with sharding

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packages/core/src/utils/shard.ts

Copilot · 2026-02-03T03:16:48Z

packages/core/src/core/rstest.ts

+          if (
+            project.config.shard &&
+            (project.config.shard.count !== rstestConfig.shard?.count ||
+              project.config.shard.index !== rstestConfig.shard?.index)
+          ) {
+            logger.error(
+              'The `shard` option is a global option and cannot be set per-project.\n' +
+                'global `shard` option:\n' +
+                `  count: ${rstestConfig.shard?.count}, index: ${rstestConfig.shard?.index}\n` +
+                `project "${project.config.name}" shard option:\n` +
+                `  count: ${project.config.shard.count}, index: ${project.config.shard.index}`,


The error message may display "count: undefined, index: undefined" when the global shard option is not set but a project has a shard config. This could be confusing. Consider updating the error message to clarify that the shard option cannot be set per-project regardless of whether it's set globally. For example: "The shard option is a global option and cannot be set per-project. Please remove the shard option from project configs."

Suggested change

if (

project.config.shard &&

(project.config.shard.count !== rstestConfig.shard?.count ||

project.config.shard.index !== rstestConfig.shard?.index)

) {

logger.error(

'The `shard` option is a global option and cannot be set per-project.\n' +

'global `shard` option:\n' +

` count: ${rstestConfig.shard?.count}, index: ${rstestConfig.shard?.index}\n` +

`project "${project.config.name}" shard option:\n` +

` count: ${project.config.shard.count}, index: ${project.config.shard.index}`,

if (project.config.shard) {

logger.error(

'The `shard` option is a global option and cannot be set per-project. ' +

'Please remove the `shard` option from project configs.',

packages/browser/src/hostController.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

9aoy added 2 commits January 29, 2026 17:34

feat: support test sharding

209e8d8

fix: index/count

b93f16b

github-actions bot added the change: feat label Jan 29, 2026

gemini-code-assist bot reviewed Jan 29, 2026

View reviewed changes

9aoy added 5 commits January 29, 2026 18:01

fix: lint

4c57e39

feat: apply shard option when list

8062d0d

Merge branch 'main' into shard

067dd9b

fix: update

d71223e

Merge branch 'shard' of https://github.com/web-infra-dev/rstest into …

554ca4b

…shard

Merge branch 'main' into shard

c6346ab

Copilot AI review requested due to automatic review settings February 3, 2026 03:10

Copilot started reviewing on behalf of 9aoy February 3, 2026 03:11 View session

Copilot AI reviewed Feb 3, 2026

View reviewed changes

9aoy and others added 2 commits February 3, 2026 11:20

chore: update logs

088710a

Update packages/browser/src/hostController.ts

070a7df

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

9aoy merged commit c29ec88 into main Feb 3, 2026
15 of 17 checks passed

9aoy deleted the shard branch February 3, 2026 05:32

fi3ework mentioned this pull request Feb 3, 2026

release: 0.8.2 #931

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feat: support test sharding#921

feat: support test sharding#921
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9aoy commented Jan 29, 2026 •

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