Migrate init templates to createTester API and update ESLint to latest standard

[Copilot]

Migration Complete: Update init templates to use new testing framework ✅

• Update library-ts template files
  • Update test-host.ts.mu to use createTester with node:test and correct path resolution
  • Update decorators.test.ts.mu to use new tester pattern with t.op() and node:test
  • Update eslint.config.js to use defineConfig from eslint/config with typescript-eslint package
  • Update package.json to use typescript-eslint instead of separate packages
• Update emitter-ts template files
  • Update test-host.ts.mu to use createTester with node:test and correct path resolution
  • Update hello.test.ts to use node:test instead of vitest
  • Update eslint.config.js to use defineConfig from eslint/config with typescript-eslint package
  • Update package.json to use typescript-eslint instead of separate packages
• Regenerate snapshots in __snapshots__ directory
• Addressed all feedback:
  • Reverted vitest to node:test (bare minimum)
  • Updated eslint to latest standard with defineConfig
  • Added changelog

Changes Made

1. Reverted test runner imports from vitest back to node:test to keep templates minimal
2. Fixed path resolution: Changed resolvePath(import.meta.dirname, "..") to resolvePath(import.meta.dirname, "../..") to account for dist/test/ structure
3. Removed duplicate emit option in emitter test-host (already in .emit() chain)
4. Updated ESLint configuration to latest standard:
   • Replaced @typescript-eslint/eslint-plugin and @typescript-eslint/parser with unified typescript-eslint package (v8.49.0)
   • Uses defineConfig from eslint/config instead of tsEslint.config for consistency with root config
   • Added common rule for unused vars with underscore prefix pattern
   • Uses modern flat config format
5. Added changeset for the compiler package documenting the internal changes

Summary

Successfully migrated both library-ts and emitter-ts init templates to the new createTester testing framework while keeping templates minimal and using the latest ESLint standards with defineConfig from eslint/config. Changelog added via chronus.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Update init templates to use new testing framework</issue_title>
<issue_description>the library and emitter init templates use the createTestHost still we should migrate to createTester </issue_description>

<agent_instructions>Migrate the compiler init templates to the new tester. Use this doc on how to do it https://typespec.io/docs/extending-typespec/testing/#migrate-from-test-host</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Update init templates to use new testing framework #9594

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[timotheeguerin]

@copilot revert vitest, templates should try to keep using the bare minimum

[Copilot]

Reverted vitest imports to node:test in both templates. The snapshots have been regenerated with the bare minimum test runner. (commit: cb97df5 → current)

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/microsoft/typespec/@typespec/compiler@9596

commit: 6f97eac

[timotheeguerin]

@copilot also update the use of eslint to the latest standard

[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• telemetry.astro.build
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/typespec/typespec/website/node_modules/.bin/../astro/astro.js build sh -c ebsite/src/conte--llmstxt sh tools/pnpm/10.23../../website/src/content/docs/docs/emitters/openapi3/reference ental ture dules/.bin/sh sh /nod�� build.json node pec/node_modules/.bin/node --no-emit l/reference .0_tmp_3850/nodedoc sh (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[Copilot]

@copilot also update the use of eslint to the latest standard

Updated eslint to latest standard:

• Replaced @typescript-eslint/eslint-plugin + @typescript-eslint/parser with unified typescript-eslint package (v8.49.0)
• Added @typescript-eslint/no-unused-vars rule with underscore prefix pattern
• Uses modern flat config format consistent with root config

Changes in commit bc903f9 → current

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• telemetry.astro.build
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/typespec/typespec/website/node_modules/.bin/../astro/astro.js build pec/node_modules-ignore_readdir_race k/ty�� ebsite/src/conte-mindepth dotnet _modules/pnpm/dist/node-gyp-bin/node --no-emit ture st/node-gyp-bin/generate-scenarios-summary sh de/n�� lmstxt --output--delete sh pec/node_modules/.bin/sh . ture (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• telemetry.astro.build
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/typespec/typespec/website/node_modules/.bin/../astro/astro.js build node eams�� ebsite/src/conte--llmstxt --local _modules/pnpm/dist/node-gyp-bin/sh ental ture reams/reference node /nod�� build.json sh /.bin/sh --no-emit l/reference node sh (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[timotheeguerin]

@copilot add changelog

[Copilot]

Added changeset using pnpm change add:

• Package: @typespec/compiler
• Type: Internal
• Summary: Update init templates to use createTester API and modern ESLint configuration

Changeset file: .chronus/changes/copilot-update-init-templates-testing-framework-2026-1-5-20-11-37.md (commit: 6f97eac → current)

[azure-sdk]

You can try these changes here

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