Stream is not updated when using map

The attached file contains two tests. The first one is based on your code and it works. The second contains a slight modification, instead of a stream of DocSnapshots the mock returns a stream of user objects, and that one hangs when checking for more than one item in emitsInOrder([]).

In the second test the stream returns the current object but no later updates.

Here is a full writeup of the issue

import 'package:equatable/equatable.dart';
import 'package:fake_cloud_firestore/fake_cloud_firestore.dart';
import 'package:flutter_test/flutter_test.dart';

import 'document_snapshot_matcher.dart';

// Model class used in the second test
class User extends Equatable {
  final String name;
  final String other;

  const User({required this.name, required this.other});

  @override
  List<Object?> get props => [name, other];

  @override
  bool get stringify => true;

  factory User.fromMap(Map<dynamic, dynamic> map) {
    return User(name: map['name'], other: map['other']);
  }

  Map<String, dynamic> toMap() {
    return {'name': name, 'other': other};
  }

  User copyWith({String? name, String? other}) {
    return User(name: name ?? this.name, other: other ?? this.other);
  }
}

void main() {
  group('Demo Only', () {});

  //This is one of the tests from the fake_cloud_firestore package.
  // https://github.com/atn832/fake_cloud_firestore/blob/master/test/fake_cloud_firestore_test.dart
  // It finishes and passes as expected.
  test('Snapshots returns a Stream of Snapshot', () async {
    final uid = 'abc';
    final instance = FakeFirebaseFirestore();
    expect(
        instance.collection('users').doc(uid).snapshots(),
        emitsInOrder([
          DocumentSnapshotMatcher('abc', null),
          DocumentSnapshotMatcher('abc', {
            'name': 'Bob',
          }),
          DocumentSnapshotMatcher('abc', {
            'name': 'Frank',
          }),
        ]));
    await instance.collection('users').doc(uid).set({
      'name': 'Bob',
    });
    await instance.collection('users').doc(uid).update({
      'name': 'Frank',
    });
  });

  // This is the same test but this time the individual DocumentSnapshots
  // are converted into User objects.
  // This test works as expected when the list passed to emitsInOrder only has
  // one element but it hangs indefinitely if the list has more elements.
  test('Returns a stream of user objects, hangs', () async {
    final uid = 'abc';
    final instance = FakeFirebaseFirestore();

    expect(
        instance
            .collection('users')
            .doc(uid)
            .withConverter<User>(
              fromFirestore: (snapshot, _) => User.fromMap(snapshot.data()!),
              toFirestore: (user, _) => user.toMap(),
            )
            .snapshots()
            .map((snapshot) => snapshot.data()),
        emitsInOrder([
          null,
          User(name: 'Bob', other: 'initial object'),
          User(name: 'Frank', other: 'modified object'),
        ]));

    await instance.collection('users').doc(uid).set({
      'name': 'Bob',
      'other': 'initial object',
    });
    await instance.collection('users').doc(uid).update({
      'name': 'Frank',
      'other': 'modified object',
    });
  });
}

atn832 / fake_cloud_firestore

Stream is not updated when using map #303