Fake Cloud Firestore

Fakes to write unit tests for Cloud Firestore. Instantiate a FakeFirebaseFirestore, then pass it around your project as if it were a FirebaseFirestore. This Fake acts like Firestore except that will only keep the data in memory. To help debug, you can use FakeFirebaseFirestore.dump() to see what's in the fake database. This is useful to set up the state of your database, then check that your UI behaves the way you expect.

This project works well with firebase_auth_mocks. If you use them together, you can even test your app with security rules. See below.

Usage

Simple example

import 'package:fake_cloud_firestore/fake_cloud_firestore.dart';

void main() {
  final instance = FakeFirebaseFirestore();
  await instance.collection('users').add({
    'username': 'Bob',
  });
  final snapshot = await instance.collection('users').get();
  print(snapshot.docs.length); // 1
  print(snapshot.docs.first.get('username')); // 'Bob'
  print(instance.dump());
}

// Prints out:
// {
//   "users": {
//     "z": {
//       "name": "Bob"
//     }
//   }
// }

See more examples at fake_cloud_firestore/test/fake_cloud_firestore_test.dart.

In a UI test

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:fake_cloud_firestore/fake_cloud_firestore.dart';
import 'package:firestore_example/main.dart';
import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';

const MessagesCollection = 'messages';

void main() {
  testWidgets('shows messages', (WidgetTester tester) async {
    // Populate the fake database.
    final firestore = FakeFirebaseFirestore();
    await firestore.collection(MessagesCollection).add({
      'message': 'Hello world!',
      'created_at': FieldValue.serverTimestamp(),
    });

    // Render the widget.
    await tester.pumpWidget(MaterialApp(
        title: 'Firestore Example', home: MyHomePage(firestore: firestore)));
    // Let the snapshots stream fire a snapshot.
    await tester.idle();
    // Re-render.
    await tester.pump();
    // // Verify the output.
    expect(find.text('Hello world!'), findsOneWidget);
    expect(find.text('Message 1 of 1'), findsOneWidget);
  });
}

See more examples at fake_cloud_firestore/example/test/widget_test.dart.

Exceptions

Based on the state

Most features automatically throw exceptions depending on the state, so you do not need to mock them. For example, calling DocumentSnapshot.get on a missing field will throw a StateError.

final firestore = FakeFirebaseFirestore();
final collection = firestore.collection('test');
final doc = collection.doc('test');
await doc.set({
  'nested': {'field': 3}
});

final snapshot = await doc.get();

expect(() => snapshot.get('foo'), throwsA(isA<StateError>()));
expect(() => snapshot.get('nested.foo'), throwsA(isA<StateError>()));

Mocking exceptions

Furthermore, some methods allow mocking exceptions manually, for example to simulate network errors. You can even set conditions on the parameters using the standard Dart matchers. Here are the methods which support mocking exceptions:

• DocumentReference.get, set, update, delete.
• Query.get.

final instance = FakeFirebaseFirestore();
final doc = instance.collection('users').doc(uid);
whenCalling(Invocation.method(#set, null))
    .on(doc)
    .thenThrow(FirebaseException(plugin: 'firestore'));
expect(() => doc.set({'name': 'Bob'}), throwsA(isA<FirebaseException>()));

For examples of how to set conditions on when to throw an exception, see firebase_auth_mocks#throwing-exceptions.

Security Rules

You can pass the security rules that you use in production in Firestore to [FakeFirebaseFirestore]. When operating on [DocumentReference] using get, set, update, or delete, [FakeFirebaseFirestore] will then check security rules and throw exceptions if access is restricted. In the example below, we restrict users/{userId} documents to their respective owners. Before they sign in, they cannot access any document inside the users collection. Once they sign in, they have access to only their own users/[uid] document.

import 'package:fake_cloud_firestore/fake_cloud_firestore.dart';
import 'package:firebase_auth_mocks/firebase_auth_mocks.dart';
import 'package:test/test.dart';

// https://firebase.google.com/docs/rules/rules-and-auth#leverage_user_information_in_rules
final authUidDescription = '''
service cloud.firestore {
  match /databases/{database}/documents {
    // Make sure the uid of the requesting user matches name of the user
    // document. The wildcard expression {userId} makes the userId variable
    // available in rules.
    match /users/{userId} {
      allow read, write: if request.auth != null && request.auth.uid == userId;
    }
  }
}''';

main() async {
  test('security rules' {
    final auth = MockFirebaseAuth();
    final firestore = FakeFirebaseFirestore(
        // Pass security rules to restrict `/users/{user}` documents.
        securityRules: authUidDescription,
        // Make MockFirebaseAuth inform FakeFirebaseFirestore of sign-in
        // changes.
        authObject: auth.authForFakeFirestore);
    // The user signs-in. FakeFirebaseFirestore knows about it thanks to
    // `authObject`.
    await auth.signInWithCustomToken('some token');
    final uid = auth.currentUser!.uid;
    // Now the user can access their user-specific document.
    expect(
        () => firestore.doc('users/$uid').set({'name': 'abc'}), returnsNormally);
    // But not anyone else's.
    expect(() => firestore.doc('users/abcdef').set({'name': 'abc'}),
        throwsException);
  });
}

See https://github.com/atn832/fake_cloud_firestore/blob/master/test/security_test.dart for more examples of security rules.

Right now we only support operations on DocumentReference. Later we will implement security checks for batch requests, collections and queries. Furthermore, we do not support timestamps and durations yet. See Fake Firebase Rules for an exhaustive list of what is and is not supported.

Resetting security rules

You can also dynamically change the security rules. This is useful if you want to first set up data without any restriction, then apply security rules for the actual tests.

https://github.com/atn832/fake_cloud_firestore/blob/0bd0b648241c0ed3e6eac2c26eef85135e3e47f9/test/security_test.dart#L82-L85

Features

• Dump the state of the fake firebase with FakeFirebaseFirestore.dump().
• Clear the fake firebase with FakeFirebaseFirestore.clearPersistence().
• Create documents and collections.
• Supports Converters.
• Create documents with collection.add or document.set.
• Batch writes and runTransaction.
• Query documents with collection.snapshots or query.get.
• Queries:
  • Filter results with query.where. The library supports equals, isGreaterThan, isGreaterThanOrEqualTo, isLessThan,isLessThanOrEqualTo, isNull, isNotEqualTo, arrayContains, arrayContainsAny, whereIn and whereNotIn.
  • Sort results with query.orderBy.
  • Limit results with query.limit, limitToLast, startAfterDocument, startAt, startAtDocument, endAt, endAtDocument, endBefore, endBeforeDocument. Note: startAnd and endAt work only on exact matches.
  • Filter with Filter, including composite filters like Filter.and and Filter.or.
  • Aggregate with query.count, query.aggregate(sum(field1), average(field2)...).
• ValueField:
  • set timestamps with FieldValue.serverTimestamp(). Optionally you can pass a Clock when instantiating FakeFirebaseFirestore to define what time gets set.
  • delete values with FieldValue.delete().
  • update numerical values with FieldValue.increment.
  • update arrays with FieldValue.arrayUnion and FieldValue.arrayRemove.
• Mock exceptions for DocumentReference.set.
• Security rules:
  • Initialize FakeFirebaseFirestore with custom security rules.
  • FakeFirebaseFirestore takes authentication state from firebase_auth_mocks into account.
  • Reset security rules.
  • DocumentReference.get, set, update and delete are protected.

Compatibility table

Features and bugs

Please file feature requests and bugs at the issue tracker.