Jest fails with universal-cookie error when frontend-base is in packages

[bradenmacdonald]

When I have frontend-base installed into the packages directory of frontend-app-instructor-dashboard, its tests fail with:

 FAIL  src/Main.test.tsx
  ● Test suite failed to run

    TypeError: _universalCookie.default is not a constructor

       8 | import { publish } from '../subscriptions';
       9 |
    > 10 | const cookies = new Cookies();
         |                 ^

Reason (thanks Claude!):

createConfig('test') sets rootDir: process.cwd() and leaves roots at its default ([rootDir]), so jest-haste-map crawls your whole app directory — including packages/frontend-base/. (It skips node_modules, so when frontend-base comes from npm as usual, its __mocks__ folders are invisible). Now that it's a real workspace directory, two of them get registered:

• packages/frontend-base/runtime/__mocks__/universal-cookie.js
• packages/frontend-base/shell/__mocks__/universal-cookie.js
  (the dist/ copies are excluded by modulePathIgnorePatterns, which is why it's exactly two.)

For a node module, a registered manual mock is applied automatically — no jest.mock() call needed. So every one of your test suites silently gets frontend-base's mock of universal-cookie, and that mock is:

module.exports = () => mockCookiesImplementation;

An arrow function has no [[Construct]], so runtime/i18n/lib.ts:10's new Cookies() throws _universalCookie.default is not a constructor.

A solution is to add roots: ['<rootDir>/src'], to jest.config.js, or to fix the mock(s) to support new properly like the code they're mocking.

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Side node: jest-haste-map is always throwing warnings about duplicate mocks, and I'm unclear why we're using it at all.