Invalid json response body at http://localhost:4000/emulators

[Wizzel1]

Hi, I am trying to setup firestore rules unit tests.

Since I am using typescript and jest for testing, I have edited your provided example a bit. This is what I have currently:

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: 'podsuite',
            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));

    });
});

My emulator runs on http://localhost:4000/ These are my rules:

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

    match /users/{userId}/salesItems/{documentId} {
      allow read: if true;
      allow write: if false;
    }

    match /users/{userId}/overviews/{documentId} {
      allow read: if true;
      allow write: if false;
    }
  }
}

When I run npm test I am getting an error :

 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

What is wrong?