Using Firebase DB Emulators, how to clear database between tests and avoid PERMISSION_DENIED?

Question

I'm following this guide to setup firebase emulators to test my realtime database security rules: https://firebase.google.com/docs/emulator-suite/connect_rtdb#clear_your_database_between_tests

At "Clear your database between tests", it suggests doing:

firebase.database().ref().set(null);

However, my security rules prevent my app from doing so.

Here's my code:

import * as firebase from '@firebase/testing';
import fs from 'fs';

const app = firebase.initializeTestApp({
  databaseName: 'myDb',
  auth: {
    uid: 'myuid',
  },
});

describe('test', () => {
  beforeEach(async () => {
    await firebase.loadDatabaseRules({
      databaseName: 'mydb',
      rules: fs.readFileSync('database.rules.json', 'utf8'),
    });
    
    await app.database().ref().set(null) // This line throws a permission denied error
  });

  afterAll(async () => {
    await Promise.all(firebase.apps().map((app) => app.delete()));
  });

  it('test', async (done) => {
    // ... //
  });
}

How can I reset my database between my tests?

Answer 1

Found a solution here

I need to use

firebase.initializeAdminApp({ databaseName: "myDb" });

to create an app that is authenticated as an admin. I can then reset the database between each test:

  const app = firebase.initializeTestApp({
    databaseName: 'myDb',
    auth: {
      uid: 'myuid',
    },
  });
  const adminApp = firebase.initializeAdminApp({ databaseName: "myDb" });
  let backup;

  beforeEach(async () => {
    await firebase.loadDatabaseRules({
      databaseName: 'myDb',
      rules: fs.readFileSync('database.rules.json', 'utf8'),
    });
    await adminApp
      .database()
      .ref('/')
      .once('value')
      .then((v) => {
        backup = v.val();
      })
  });

  afterEach(async ()=>{
    await adminApp.database().ref('/').set(backup);
  })