[TEST] NoSuchMethodError: The getter 'uid' was called on null. Receiver: null Tried calling: uid

I've tried fixing using MockFirebaseAuth.instance by defining get in MockFirebaseAuth + initializing FirebaseApp with TestWidgetsFlutterBinding.

Problem code posted below...

firebase_flutter_repository_test.dart:

import 'dart:async';

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_flutter_repository/firebase_user_repository.dart';
import 'package:custom_repository_core/custom_repository_core.dart';
import 'package:mockito/mockito.dart';
import 'package:test/test.dart';

void main() {
  group('FirebaseUserRepository', () {
    test('should log the user in anonymously', () async {
      final auth = MockFirebaseAuth();
      final repository = FirebaseUserRepository(auth);

      when(auth.signInAnonymously())
          .thenAnswer((_) => Future.value(MockUserCredential()));

      final entity = await repository.login();

      expect(entity, TypeMatcher<UserEntity>());
    });
  });
}

class MockFirebaseAuth extends Mock implements FirebaseAuth {}

class MockFirestore extends Mock implements FirebaseFirestore {}

class MockUserCredential extends Mock implements UserCredential {}

firebase_user_repository.dart:

import 'dart:async';

import 'package:firebase_auth/firebase_auth.dart';
import 'package:custom_repository_core/custom_repository_core.dart';

class FirebaseUserRepository implements UserRepository {
  final FirebaseAuth auth;

  const FirebaseUserRepository(this.auth);

  @override
  Future<UserEntity> login() async {
    final firebaseUser = await auth.signInAnonymously();

    return UserEntity(
      id: firebaseUser.user.uid,      /// firebaseUser.user shows up as null
      displayName: firebaseUser.user.displayName,
    );
  }
}

pubspec.yaml

environment:
  sdk: '>=2.0.0 <3.0.0'

dependencies:
  flutter:
    sdk: flutter
  custom_repository_core:
    path: ../custom_repository_core
  firebase_auth: ^1.1.3
  cloud_firestore: ^2.0.0

dev_dependencies:
  test:
  mockito:
  flutter_test:
    sdk: flutter

flutter: