philmod / firestore-jest-mock

Jest Helper library for mocking Cloud Firestore

Mock Firestore

Jest Mock for testing Google Cloud Firestore

A simple way to mock calls to Cloud Firestore, allowing you to assert that you are requesting data correctly.

This is not a pseudo-database -- it is only for testing you are interfacing with firebase/firestore the way you expect.

Table of Contents

• Mock Firestore
  • Table of Contents
  • What's in the Box
  • Installation
  • Usage
    • mockFirebase
    • What would you want to test?
    • Don't forget to reset your mocks
      • I wrote a where clause, but all the records were returned!
    • Functions you can test
      • Firestore
      • Auth
  • Contributing
  • Code of Conduct
  • About Upstatement

What's in the Box

This library provides an easy to use mocked version of firestore.

Installation

With npm:

npm install --save-dev firestore-jest-mock

With yarn:

yarn add --dev firestore-jest-mock

Usage

mockFirebase

The default method to use is mockFirebase, which returns a jest mock, overwriting firebase and firebase-admin. It accepts an object with two pieces:

• database -- A mock of your collections
• currentUser -- (optional) overwrites the currently logged in user

Example usage:

const { mockFirebase } = require('firestore-jest-mock');
// Create a fake firestore with a `users` and `posts` collection
mockFirebase({
  database: {
    users: [
      { id: 'abc123', name: 'Homer Simpson' },
      { id: 'abc456', name: 'Lisa Simpson' },
    ],
    posts: [{ id: '123abc', title: 'Really cool title' }],
  },
});

This will populate a fake database with a users and posts collection.

Now you can write queries or requests for data just as you would with firestore:

test('testing stuff', () => {
  const firebase = require('firebase'); // or import firebase from 'firebase';
  const db = firebase.firestore();

  db.collection('users')
    .get()
    .then(userDocs => {
      // write assertions here
    });
});

What would you want to test?

The job of the this library is not to test firestore, but to allow you to test your code without hitting firebase. Take this example:

function maybeGetUsersInState(state) {
  const query = firestore.collection('users');

  if (state) {
    query = query.where('state', '==', state);
  }

  return query.get();
}

We have a conditional query here. If you pass state to this function, we will query against it; otherwise, we just get all of the users. So, you may want to write a test that ensures you are querying correctly:

const { mockFirebase } = require('firestore-jest-mock');

// Import the mock versions of the functions you expect to be called
const { mockCollection, mockWhere } = require('firestore-jest-mock/mocks/firestore');
describe('we can query', () => {
  mockFirebase({
    database: {
      users: [
        { id: 'abc123', name: 'Homer Simpson' },
        { id: 'abc456', name: 'Lisa Simpson' },
      ],
    },
  });

  test('query with state', async () => {
    await maybeGetUsersInState('alabama');

    // Assert that we call the correct firestore methods
    expect(mockCollection).toHaveBeenCalledWith('users');
    expect(mockWhere).toHaveBeenCalledWith('state', '==', 'alabama');
  });

  test('no state', async () => {
    await maybeGetUsersInState();

    // Assert that we call the correct firestore methods
    expect(mockCollection).toHaveBeenCalledWith('users');
    expect(mockWhere).not.toHaveBeenCalled();
  });
});

In this test, we don't necessarily care what gets returned from firestore (it's not our job to test firestore), but instead we try to assert that we built our query correctly.

If I pass a state to this function, does it properly query the users collection?

That's what we want to answer.

Don't forget to reset your mocks

In jest, mocks will not reset between test instances unless you specify them to. This can be an issue if you have two tests that make an asseration against something like mockCollection. If you call it in one test and assert that it was called in another test, you may get a false positive.

Luckily, jest offers a few methods to reset or clear your mocks.

• clearAllMocks() clears all the calls for all of your mocks. It's good to run this in a beforeEach to reset between each test

jest.clearAllMocks();

• mockClear() this resets one specific mock function

mockCollection.mockClear();

I wrote a where clause, but all the records were returned!

The where clause in the mocked firestore will not actually filter the data at all. We are not recreating firestore in this mock, just exposing an API that allows us to write assertions. It is also not the job of the developer (you) to test that firestore filtered the data appropriately. Your application doesn't double-check firestore's response -- it trusts that it's always correct!

Functions you can test

Firestore

Method	Use	Method in Firestore
mockCollection	Assert the correct collection is being queried	collection
mockCollectionGroup	Assert the correct collectionGroup is being queried	collectionGroup
mockDoc	Assert the correct record is being fetched by id. Tells the mock you are fetching a single record	doc
mockWhere	Assert the correct query is written. Tells the mock you are fetching multiple records	where
mockBatch	Assert batch was called	batch
mockBatchDelete	Assert correct refs are passed	batch delete
mockBatchCommit	Assert commit is called. Returns a promise	batch commit
mockGet	Assert get is called. Returns a promise resolving either to a single doc or querySnapshot	get
mockGetAll	Assert correct refs are passed. Returns a promise resolving to array of docs.	getAll
mockUpdate	Assert correct params are passed to update. Returns a promise	update
mockAdd	Assert correct params are passed to add. Returns a promise resolving to the doc with new id	add
mockSet	Assert correct params are passed to set. Returns a promise	set
mockDelete	Assert delete is called on ref. Returns a promise	delete
mockOrderBy	Assert correct field is passed to orderBy	orderBy
mockLimit	Assert limit is set properly	limit

Auth

Method	Use	Method in Firebase
mockCreateUserWithEmailAndPassword	Assert correct email and password are passed. Returns a promise	createUserWithEmailAndPassword
mockDeleteUser	Assert correct id is passed to delete method. Returns a promise	deleteUser
mockSendVerificationEmail	Assert request for verification email was sent. Lives on the currentUser	sendVerificationEmail
mockSignInWithEmailAndPassword	Assert correct email and password were passed. Returns a promise	signInWithEmailAndPassword
mockSendPasswordResetEmail	Assert correct email was passed.	sendPasswordResetEmail
mockVerifyIdToken	Assert correct token is passed. Returns a promise	verifyIdToken

Contributing

We welcome all contributions to our projects! Filing bugs, feature requests, code changes, docs changes, or anything else you'd like to contribute are all more than welcome! More information about contributing can be found in the contributing guidelines.

To get set up, simply clone this repository and npm install!

Code of Conduct

Upstatement strives to provide a welcoming, inclusive environment for all users. To hold ourselves accountable to that mission, we have a strictly-enforced code of conduct.

About Upstatement

Upstatement is a digital transformation studio headquartered in Boston, MA that imagines and builds exceptional digital experiences. Make sure to check out our services, work, and open positions!