@firebase/rules-unit-testing stalls on dbRef.set() with package.json settings jest.preset:"jest-expo" but succeeds with jest.preset:"ts-jest"

[DrStoop]

Operating System

Linux 6.8 Ubuntu 24.04.1 LTS 24.04.1 LTS (Noble Numbat)

Environment (if applicable)

Expo, React Native

Firebase SDK Version

@firebase/[email protected]

Firebase SDK Product(s)

Database

Project Tooling

React-Native app managed with Expo for Android & iOS:

Minimal reproducible example

https://github.com/DrStoop/expoWithJestFirebaseDatabaseEmulator.git

Detailed Problem Description

Minimal reproducible example

https://github.com/DrStoop/expoWithJestFirebaseDatabaseEmulator.git

What platform(s) does this occur on?

Jest testing environment with jest-expo preset

Summary

jest-expo preset causes dbRef.set() to stall when testing database rules with @firebase/rules-unit-testing

I am using firebase realtime database in my expo app and am writing database rules unit tests using @firebase/rules-unit-testing and the firebase emulator locally. I encountered the issue that the command await assertSucceeds(dbRef.set(5)); in __tests__/firebaseRealtimeDatabaseRules.test.ts stalls (infinitely) in my test. I created a minimal reproducible example and could nail the cause of the stalling down to the jest.preset: "jest-expo" in package.json. The test passes without stalling when setting it to jest.preset: "ts-jest" and it throws a timeout fail when set to jest.preset:"jest-expo" (also with increases timeouts):

 FAIL  __tests__/firebaseRealtimeDatabaseRules.test.ts (5.539 s)
  Can read write
    ✕  should succeed (5012 ms)

  ● Can read write ›  should succeed

    thrown: "Exceeded timeout of 5000 ms for a test.
    Add a timeout value to this test to increase the timeout, if this is a long-running test. See https://jestjs.io/docs/api#testname-fn-timeout."

      41 |   });
      42 |
    > 43 |   it(` should succeed`, async () => {
         |   ^
      44 |     const dbRef = database.ref(`authed`);
      45 |     // const unauthedRef = unauthedUser.database().ref(`unauthed`);
      46 |     const valueChange = dbRef.on("value", (snapshot) => {

      at it (__tests__/firebaseRealtimeDatabaseRules.test.ts:43:3)
      at Object.describe (__tests__/firebaseRealtimeDatabaseRules.test.ts:15:1)

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 total
Snapshots:   0 total
Time:        5.881 s

I'm running the firebase database emulator with initial command:

$ firebase emulators:start --only database --project database


i  emulators: Starting emulators: database
i  database: Database Emulator logging to database-debug.log

┌─────────────────────────────────────────────────────────────┐
│ ✔  All emulators ready! It is now safe to connect your app. │
│ i  View Emulator UI at http://127.0.0.1:4000/               │
└─────────────────────────────────────────────────────────────┘

┌──────────┬────────────────┬────────────────────────────────┐
│ Emulator │ Host:Port      │ View in Emulator UI            │
├──────────┼────────────────┼────────────────────────────────┤
│ Database │ 127.0.0.1:9000 │ http://127.0.0.1:4000/database │
└──────────┴────────────────┴────────────────────────────────┘
  Emulator Hub running at 127.0.0.1:4400
  Other reserved ports: 4500

Issues? Report them at https://github.com/firebase/firebase-tools/issues and attach the *-debug.log files.

jest-expo preset

• The test script initially connects to the database emulator via localhost:9000 and initializes the database rules.
• The dbRef.set(value) method does not send the value itself to the database and the database does not set any values, see emulator debug log:

[2025-01-09T17:39:59.546Z] 19:39:59.546 [NamespaceSystem-blocking-namespace-operation-dispatcher-9] INFO com.firebase.core.namespace.StateManager - Namespace database-default-rtdb status Active to Active
 {"metadata":{"emulator":{"name":"database"},"message":"19:39:59.546 [NamespaceSystem-blocking-namespace-operation-dispatcher-9] INFO com.firebase.core.namespace.StateManager - Namespace database-default-rtdb status Active to Active\n"}}

• Also dbRef.set() methods show the same issue.

ts-jest preset

• The test script also connects tot the database emulator, updates the database rules and successfully sends the value with dbRef.set(value), see database debug log:

[2025-01-09T18:09:53.068Z] 20:09:53.067 [NamespaceSystem-blocking-namespace-operation-dispatcher-10] INFO com.firebase.core.namespace.StateManager - Namespace database-default-rtdb status Active to Active
 {"metadata":{"emulator":{"name":"database"},"message":"20:09:53.067 [NamespaceSystem-blocking-namespace-operation-dispatcher-10] INFO com.firebase.core.namespace.StateManager - Namespace database-default-rtdb status Active to Active\n"}}
[2025-01-09T18:09:53.098Z] 20:09:53.098 [FirebaseWorkerPool-1-2] WARN com.firebase.server.forge.App$ - Received service account token eyJh...fX0., assuming ownership.
 {"metadata":{"emulator":{"name":"database"},"message":"20:09:53.098 [FirebaseWorkerPool-1-2] WARN com.firebase.server.forge.App$ - Received service account token eyJh...fX0., assuming ownership.\n"}}

• The database emulator receives the value (5) and displays it in the UI:
  

Question

Why is the jest preset "jest-expo" interfering with @firebase/rules-unit-testing and how can it be fixed? Or am I just missing something? Changing the preset to "ts-jest" is not an option unless I would run database rules unit tests in isolation in a separate project (which is also not really an option).

Thanks in advance!

Note

As this seems like a bug in the interface between an Expo preset jest-expo and the firebase emulator, I posted this issue already in the expo repository, but without getting feedback. So I'm hoping to get some hints from the firebase community here, THX!

Environment

expo-env-info 1.2.1 environment info:
    System:
      OS: Linux 6.8 Ubuntu 24.04.1 LTS 24.04.1 LTS (Noble Numbat)
      Shell: 5.2.21 - /bin/bash
    Binaries:
      Node: 20.13.0 - ~/.nvm/versions/node/v20.13.0/bin/node
      Yarn: 1.22.22 - ~/.nvm/versions/node/v20.13.0/bin/yarn
      npm: 10.9.0 - ~/.nvm/versions/node/v20.13.0/bin/npm
    npmPackages:
      expo: ~52.0.24 => 52.0.24 
      expo-router: ~4.0.16 => 4.0.16 
      react: 18.3.1 => 18.3.1 
      react-dom: 18.3.1 => 18.3.1 
      react-native: 0.76.5 => 0.76.5 
      react-native-web: ~0.19.13 => 0.19.13 
    npmGlobalPackages:
      eas-cli: 13.3.0
    Expo Workflow: managed

Expo Doctor Diagnostics

Enabled experimental React Native Directory checks. Unset the EXPO_DOCTOR_ENABLE_DIRECTORY_CHECK environment variable to disable this check.
✔ Check package.json for common issues
✔ Check Expo config for common issues
✔ Check native tooling versions
✔ Check if the project meets version requirements for submission to app stores
✔ Check for common project setup issues
✔ Check dependencies for packages that should not be installed directly
✔ Check for app config fields that may not be synced in a non-CNG project
✔ Check for issues with Metro config
✔ Check npm/ yarn versions
✔ Validate packages against React Native Directory package metadata
✔ Check Expo config (app.json/ app.config.js) schema
✔ Check for legacy global CLI installed locally
✔ Check that native modules do not use incompatible support packages
✔ Check that packages match versions required by installed Expo SDK
✔ Check that native modules use compatible support package versions for installed Expo SDK

Didn't find any issues with the project!

Steps and code to reproduce issue

Minimal reproducible example

https://github.com/DrStoop/expoWithJestFirebaseDatabaseEmulator.git

Steps

• Install the project with npm install
• Install firebase emulator
• Run firebase realtime database emulator with firebase emulators:start --only database --project database
• Run the test with npm run test will fail as this issue describes due to the {"jest":{"preset": "jest-expo"}}
• Change the preset to {"jest":{"preset": "ts-jest"}} and kill & re-run the test with npm run test and the test will succeed without errors because it's not relying on jest-expo preset anymore

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[dlarocque]

Hey @DrStoop, we'd be glad to investigate whether this is an issue with our SDK. Since we are not familiar with jest-expo, it is challenging for us to pinpoint which environment changes it makes cause this issue. If this issue could be narrowed down to a specific environment setting, it would really help us confirm whether we can do something to fix this on our end.

[DrStoop]

Hi @dlarocque, thanks for getting back to me. I get your point, that's why I also raised this issue in the expo repository first - unfortunately without response so far. I will be working on this problem and update you on the results if the issue is on the firebase or expo side. Thanks for now!

[hsubox76]

Just to be clear, the information we'd need to pinpoint if this is a Firebase issue or not is basically "what does the jest-expo preset do?" Which may be an easier answer to get than presenting the entire bug to the Expo team and asking them to look into it as a whole. I went into the Expo repo trying to find out if it was a simple JSON config "extend" but it seems a bit more complicated than that (https://github.com/expo/expo/tree/main/packages/jest-expo) as there's a lot of code that eventually leads to the final jest config somewhere. If someone could quickly give a TLDR of how the jest-expo preset differs from ts-jest (or some other preset that works for you), that would really increase the odds of finding out what's going wrong.

[DrStoop]

Thanks @hsubox76 for looking into the issue. That's a good point comparing ts-jest with jest-expo to figure out which differences could cause the problem. After a quick look, ts-jest might not help reducing the "region of interest" though as ts-jest "simply" converts ts-files into js-files, whereas jest-expo seems to do a lot of mocking and adjusting environment configs to simulate react-native/mobile envs instead of node.js... at least that's my rough idea. So the problem could still be anywhere. My best guess right now is that a function or module that @firebase/rules-unit-testing depends on is being mocked by jest-expo, specifically a function or module that the dbRef.set() function is using. But I have tried jest.unmocking & jest.requireAcutaling all kind of modules, but without success so far. If I'm right the issue is on the jest-expo side. I will update you on any progress. thx again.