typescript - 在模擬器中測試 firestore 規則失敗，原因：JSON 在位置 0 發生意外的符號 <

我正在嘗試為我的 Firestore 規則設置單元測試。

由於我正在使用 TypeScript 和 Jest 進行測試，我試著編輯這個範例，但似乎我漏掉了什麼。

這是我的檔案：

import { readFileSync } from 'fs-extra'

import * as firebase from '@firebase/rules-unit-testing'
import { getDoc, setDoc, setLogLevel } from 'firebase/firestore'

describe('Firestore Rules', () => {
    let testEnv: firebase.RulesTestEnvironment;
    beforeAll(async () => {
        testEnv = await firebase.initializeTestEnvironment({
            firestore: { rules: readFileSync('../firestore.rules', 'utf8') },
            projectId: 'myproject',
            hub: { host: 'localhost', port: 4000 },
        });
    });

    afterAll(async () => {
        await testEnv.cleanup();
    });

    beforeEach(async () => {
        await testEnv.clearFirestore();
    });


    test('noone should have access to user document', async function () {
        // Setup: Create documents in DB for testing (bypassing Security Rules).
        await testEnv.withSecurityRulesDisabled(async (context) => {
            const testdoc = context.firestore().collection('users').doc('user1234');
            await setDoc(testdoc, { test: 'test1' });
        });

        const unauthedDb = testEnv.unauthenticatedContext().firestore();

        // Then test security rules by trying to read it using the client SDK.
        const testdoc = unauthedDb.collection('users').doc('user1234');

        await firebase.assertFails(getDoc(testdoc));

    });
});

這是我的規則檔案：

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /users/{userId} {
       allow read, write: if false;
    }
  }
}

當我嘗試運行測試時，我收到此錯誤：

 FAIL  src/tests/rules.test.ts
  ●  Firestore Rules › noone should have access to user document

    FetchError: invalid json response body at http://localhost:4000/emulators reason: Unexpected token < in JSON at position 0

      at node_modules/@firebase/rules-unit-testing/node_modules/node-fetch/lib/index.js:272:32

那我到底做錯了什麼？