Fix failing tests by migrating Jest and entire codebase to native ESM

[Copilot]

Summary

The @actions/core, @actions/artifact, and @actions/github packages were upgraded to versions that are ESM-only (no CommonJS build). This broke the Jest test suite. In addition, eslint-plugin-github@6 requires eslint@^8||^9, conflicting with the previously used eslint@10.

Root Cause

ESM-only packages cannot be require()'d by Jest's CJS module system. An earlier attempt at using useESM: true in ts-jest failed for two reasons:

1. resetModules: true reset the module registry before each individual test, making module-level jest.mocked() references stale in ESM mode.
2. __dirname / __filename are not available in ES modules.

Solution

Migrated the entire project to native ESM: ts-jest now compiles with useESM: true, the test script uses NODE_OPTIONS=--experimental-vm-modules, and tsconfig.json overrides to module: ESNext + moduleResolution: Bundler so import.meta.dirname is valid while ncc still bundles correctly. All __dirname / __filename usages are replaced with import.meta.dirname / import.meta.filename. eslint is downgraded to ^9 to satisfy eslint-plugin-github@6's peer requirement.

Because moduleNameMapper resolves stubs before the module graph is built, it is used for all packages that cannot be intercepted by late-hoisted jest.mock calls in ESM VM-modules mode (@actions/core, @actions/artifact, @actions/github, and adm-zip).

Changes

New / replaced files

• __mocks__/@actions/core.ts — ESM TypeScript stub; commonly-used functions (getInput, setFailed, warning, error, info, debug, setOutput, summary, etc.) are exported as jest.fn() with real default implementations so snapshot tests capture the correct ::command:: stdout format and tests can verify calls via jest.mocked() without per-file factories. setFailed intentionally does not set process.exitCode to avoid affecting Jest's exit handling.
• __mocks__/@actions/artifact.ts — ESM TypeScript stub; DefaultArtifactClient exported as jest.fn().
• __mocks__/@actions/github.ts — ESM TypeScript stub; getOctokit exported as jest.fn().
• __mocks__/adm-zip.ts — New ESM stub; adm-zip sits in a static import chain, so a jest.mock factory cannot be hoisted early enough in ESM VM-modules mode. moduleNameMapper pre-resolves it before the module graph is built.
• tsconfig.test.json — Removed (no longer needed; a single tsconfig.json covers everything).

Modified files

• jest.config.js — Removed resetModules; added extensionsToTreatAsEsm: ['.ts'], useESM: true, and adm-zip entry in moduleNameMapper.
• package.json — Test script uses NODE_OPTIONS=--experimental-vm-modules jest; eslint downgraded to ^9.
• tsconfig.json — Overrides module: ESNext and moduleResolution: Bundler.
• src/utils.ts — __dirname replaced with path.dirname(fileURLToPath(import.meta.url)); jpath cast retained.
• eslint.config.mjs — Added __mocks__/ to eslint ignores.
• .gitignore — Added patterns for temp test files.
• __tests__/functions.test.ts — Removed per-file jest.mock('@actions/core') factory; replaced all jest.spyOn(core, 'setFailed') calls with jest.mocked(core.setFailed).mockImplementation(...) (ESM module namespace properties are read-only so spyOn cannot replace them).
• __tests__/run.test.ts — Removed per-file jest.mock factories; replaced jest.mock('../src/utils', factory) with jest.unstable_mockModule (the ESM-native async mock API). Real util functions are imported via static imports at the top of the file and passed as closures into the factory (avoids circular load OOM). { run } is imported dynamically in beforeAll so it sees the mocked utils.
• __tests__/artifacts.test.ts — Removed broken per-test jest.mock factories (now handled entirely by the stubs).

Test Results

Test Suites: 4 passed, 4 total
Tests:       87 passed, 87 total
Snapshots:   25 passed, 25 total

Security

CodeQL scan: 0 alerts

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[stacklane-pr-stack-visualizer]

🧱 Stack PR · Base of stack

Stack Structure:

• Fix failing tests by migrating Jest and entire codebase to native ESM #159 copilot/fix-failing-tests-after-package-update ← YOU ARE HERE

[tm1000]

@copilot ci fails with the following:

npm error code ERESOLVE
npm error ERESOLVE could not resolve
npm error
npm error While resolving: eslint-plugin-github@6.0.0
npm error Found: eslint@10.0.3
npm error node_modules/eslint
npm error   dev eslint@"^10.0.3" from the root project
npm error   peer eslint@"^6.0.0 || ^7.0.0 || >=8.0.0" from @eslint-community/eslint-utils@4.9.1
npm error   node_modules/@eslint-community/eslint-utils
npm error     @eslint-community/eslint-utils@"^4.9.1" from @typescript-eslint/utils@8.57.1
npm error     node_modules/@typescript-eslint/utils
npm error       @typescript-eslint/utils@"8.57.1" from @typescript-eslint/eslint-plugin@8.57.1
npm error       node_modules/@typescript-eslint/eslint-plugin
npm error         @typescript-eslint/eslint-plugin@"^8.0.0" from eslint-plugin-github@6.0.0
npm error         node_modules/eslint-plugin-github
npm error         2 more (eslint-plugin-jest, typescript-eslint)
npm error       3 more (@typescript-eslint/type-utils, eslint-plugin-jest, typescript-eslint)
npm error     @eslint-community/eslint-utils@"^4.8.0" from eslint@10.0.3
npm error   13 more (@eslint/js, @typescript-eslint/eslint-plugin, ...)
npm error
npm error Could not resolve dependency:
npm error peer eslint@"^8 || ^9" from eslint-plugin-github@6.0.0
npm error node_modules/eslint-plugin-github
npm error   dev eslint-plugin-github@"^6.0.0" from the root project
npm error
npm error Conflicting peer dependency: eslint@9.39.4
npm error node_modules/eslint
npm error   peer eslint@"^8 || ^9" from eslint-plugin-github@6.0.0
npm error   node_modules/eslint-plugin-github
npm error     dev eslint-plugin-github@"^6.0.0" from the root project
npm error
npm error Fix the upstream dependency conflict, or retry
npm error this command with --force or --legacy-peer-deps
npm error to accept an incorrect (and potentially broken) dependency resolution.
npm error
npm error
npm error For a full report see:
npm error /home/runner/.npm/_logs/2026-03-20T03_13_01_933Z-eresolve-report.txt
npm error A complete log of this run can be found in: /home/runner/.npm/_logs/2026-03-20T03_13_01_933Z-debug-0.log

[Copilot]

Pull request overview

This PR restores the repo’s CJS-based Jest test suite after upgrading @actions/core, @actions/artifact, and @actions/github to ESM-only versions by routing tests through CJS-compatible stubs and updating Jest/ts-jest configuration accordingly.

Changes:

• Added CJS stub implementations for @actions/* modules and mapped them via jest.config.js moduleNameMapper.
• Updated Jest/ts-jest TypeScript configuration and adjusted tests for Jest 30 typing/spy behavior changes.
• Addressed a TypeScript typing change in fast-xml-parser v5 by adjusting the isArray callback handling.

Reviewed changes

Copilot reviewed 8 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tsconfig.test.json	Adds a dedicated TS config for tests to compile src/ and __tests__/ together.
jest.config.js	Configures ts-jest to use tsconfig.test.json and maps @actions/* imports to local CJS stubs.
__mocks__/@actions/core.js	Introduces a CJS stub for @actions/core, including summary and command behaviors used by tests.
__mocks__/@actions/artifact.js	Adds a minimal @actions/artifact CJS stub exporting DefaultArtifactClient.
__mocks__/@actions/github.js	Adds a minimal @actions/github CJS stub exporting getOctokit and context.
__tests__/run.test.ts	Mocks @actions/core in-test with jest.fn() APIs and switches assertions to jest.mocked(...) instead of spyOn.
__tests__/functions.test.ts	Adds an @actions/core mock wrapper with __esModule: true and updates setFailed mock typings.
__tests__/artifacts.test.ts	Adds explicit jest.fn<...>() generics to avoid never inference with mockResolvedValue (Jest 30).
src/utils.ts	Resolves a TS type error from fast-xml-parser v5 by asserting jpath as string when calling inArray.
package-lock.json	Updates lockfile metadata consistent with dependency updates (e.g., TypeScript marked as dev).

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[Copilot]

getMultilineInput() splits only on \n, which will leave trailing \r characters when inputs contain Windows-style \r\n newlines. This diverges from @actions/core behavior and can cause subtle test differences. Consider splitting on /\r?\n/ instead.

Suggested change

	.split('\n')
	.split(/\r?\n/)

[Copilot]

When GITHUB_OUTPUT is set, setOutput() appends name=value directly. The official file-command format uses a delimiter (name<<EOF ... EOF) to safely support multiline values and special characters; writing raw name=value can produce incorrect outputs if a value contains newlines. Consider implementing the delimiter-based format for GITHUB_OUTPUT (and similarly for GITHUB_ENV/GITHUB_STATE if these helpers are meant to be faithful).

[Copilot]

Casting jpath to string sidesteps the updated fast-xml-parser typing (string | Matcher). If jpath is ever not a string at runtime, this will silently compare non-strings inside inArray(). Consider guarding with typeof jpath === 'string' ? inArray(jpath, ...) : false to keep type-safety without relying on an assertion.

[Copilot]

@copilot ci fails with the following:

...

Fixed in commit 011084e. The eslint peer conflict (eslint@10 vs eslint-plugin-github@6 needing ^8||^9) was already resolved by the eslint downgrade in the previous commit. On top of that, this commit fully converts Jest to native ESM, which is what was originally requested.

Why useESM didn't work the first time:

1. resetModules: true was resetting the module registry before each individual test, making module-level jest.mocked() references stale in ESM
2. __dirname is not available in ESM modules

What changed now:

• All __mocks__/@actions/*.js (CJS) → __mocks__/@actions/*.ts (ESM TypeScript) — functions like setFailed/warning are now jest.fn() with real default implementations so tests can verify calls without needing per-file factories
• __mocks__/adm-zip.ts added — adm-zip is in a static import chain so jest.mock(factory) can't be hoisted early enough in ESM VM-modules mode; moduleNameMapper pre-resolves it before the module graph is built
• jest.mock('../src/utils', factory) in run.test.ts replaced with jest.unstable_mockModule (the ESM-native mock API) + dynamic import('../src/functions') in beforeAll
• jest.spyOn(core, 'setFailed') replaced with jest.mocked(core.setFailed).mockImplementation(...) — ESM module namespace properties are read-only
• __dirname → import.meta.dirname everywhere; tsconfig.json overrides module: ESNext so ncc/webpack still bundles correctly

Security summary: CodeQL scan: 0 alerts.

[github-actions]

Code Coverage Report

Package	Base Coverage	New Coverage	Difference
functions.ts	🟢 94.67%	🟢 94.52%	🔴 -0.15%
reports/clover/parser/index.ts	🟢 96.34%	🟢 96.25%	🔴 -0.09%
reports/clover/types/index.ts	🟢 100%	🟢 100%	⚪ 0%
reports/cobertura/parser/index.ts	🟢 76.47%	🟢 75.9%	🔴 -0.57%
reports/cobertura/types/index.ts	🟢 100%	🟢 100%	⚪ 0%
utils.ts	🟢 94.23%	🟢 93.79%	🔴 -0.44%
Overall Coverage	🟢 93.24%	🟢 92.89%	🔴 -0.35%

Minimum allowed coverage is 70%, this run produced 92.89%