[2.x] Frontend testing setup from docs is unusable for standalone (Composer-installed) extensions — @flarum/jest-config depends on unpublished @flarum/core

[imorland]

Summary

The frontend testing docs present a setup that works inside the flarum/framework monorepo but cannot run in a standalone, Composer-installed extension. The docs don't state this limitation; they imply the flow works for any extension (you're told to install only @flarum/jest-config, never @flarum/core).

Root cause

@flarum/jest-config resolves core from the @flarum/core npm package, which is not published to the registry (yarn add @flarum/core → 404). It only exists in the monorepo as a workspace symlink.

• setup-env.js (runs for every test via setupFilesAfterEnv):

  import mixin from '@flarum/core/src/common/utils/mixin';
  import ExportRegistry from '@flarum/core/src/common/ExportRegistry';

• src/boostrap/forum.js / common.js (the documented bootstrapForum()):

  import app from '@flarum/core/src/forum/app';
  import { makeUser } from '@flarum/core/tests/factory';
  // ...
  fs.readFileSync('../locale/core.yml', 'utf8')

Reproduction

In a standalone extension, follow the docs exactly (yarn add -D @flarum/jest-config, jest.config.cjs = require('@flarum/jest-config')(), add the test script + "type": "module"), write one trivial test, and run yarn test:

1. @flarum/core can't be installed (404), so the bootstrap imports are unresolvable.
2. Mapping @flarum/core/* → the Composer-vendored vendor/flarum/core/js lets resolution proceed, but Jest does not transform that TypeScript (it's outside the js/ rootDir), so setup-env fails before any test with SyntaxError: Unexpected token ':' — even for a test that imports nothing.
3. bootstrapForum() additionally needs @flarum/core/tests/factory and ../locale/core.yml, whose relative paths only resolve inside the monorepo.

Corroboration: flarum/framework's own messages extension ships the jest config but has empty tests/unit and tests/integration dirs.

What currently is possible standalone

Pure-logic unit tests work if you skip the core-importing global setup and map the specific core utilities you use to their underlying npm packages (e.g. flarum/common/utils/Stream → mithril/stream). Component/app-bootstrapped tests do not.

Suggested resolutions (any one)

• Publish @flarum/core to npm (including src/, tests/factory, and locale/) so extensions can depend on it.
• Make @flarum/jest-config resolve core from the Composer-vendored path (vendor/flarum/core/js) and ensure that source is transformed.
• At minimum, document the prerequisite/limitation: that frontend tests (especially bootstrap*) currently require developing within the monorepo, and which subset works standalone.

Environment

@flarum/jest-config@2.0.0, standalone extension with flarum/core: ^2.0.0-rc.2 (Composer), vendor/flarum/core/js present, Node 24 / Yarn 1.22.