chore(mobile): Favorite provider unit test (#1874)

* Favorite provider tests

* Remove unused mock

* Add setUp function to avoid duplicate code

mobile/test/favorite_provider_test.dart

@@ -0,0 +1,104 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:immich_mobile/modules/favorite/providers/favorite_provider.dart';
+import 'package:immich_mobile/shared/models/asset.dart';
+import 'package:immich_mobile/shared/providers/asset.provider.dart';
+import 'package:mockito/annotations.dart';
+import 'package:mockito/mockito.dart';
+
+@GenerateNiceMocks([
+  MockSpec<AssetsState>(),
+  MockSpec<AssetNotifier>(),
+])
+import 'favorite_provider_test.mocks.dart';
+
+Asset _getTestAsset(String id, bool favorite) {
+  return Asset(
+    remoteId: id,
+    deviceAssetId: '',
+    deviceId: '',
+    ownerId: '',
+    fileCreatedAt: DateTime.now(),
+    fileModifiedAt: DateTime.now(),
+    durationInSeconds: 0,
+    fileName: '',
+    isFavorite: favorite,
+  );
+}
+
+void main() {
+  group("Test favoriteProvider", () {
+
+    late MockAssetsState assetsState;
+    late MockAssetNotifier assetNotifier;
+    late ProviderContainer container;
+    late StateNotifierProvider<FavoriteSelectionNotifier, Set<String>> testFavoritesProvider;
+
+    setUp(() {
+      assetsState = MockAssetsState();
+      assetNotifier = MockAssetNotifier();
+      container = ProviderContainer();
+
+      testFavoritesProvider =
+          StateNotifierProvider<FavoriteSelectionNotifier, Set<String>>((ref) {
+            return FavoriteSelectionNotifier(
+              assetsState,
+              assetNotifier,
+            );
+          });
+    },);
+
+    test("Empty favorites provider", () {
+      when(assetsState.allAssets).thenReturn([]);
+      expect(<String>{}, container.read(testFavoritesProvider));
+    });
+
+    test("Non-empty favorites provider", () {
+      when(assetsState.allAssets).thenReturn([
+        _getTestAsset("001", false),
+        _getTestAsset("002", true),
+        _getTestAsset("003", false),
+        _getTestAsset("004", false),
+        _getTestAsset("005", true),
+      ]);
+
+      expect(<String>{"002", "005"}, container.read(testFavoritesProvider));
+    });
+
+    test("Toggle favorite", () {
+      when(assetNotifier.toggleFavorite(null, false))
+          .thenAnswer((_) async => false);
+
+      final testAsset1 = _getTestAsset("001", false);
+      final testAsset2 = _getTestAsset("002", true);
+
+      when(assetsState.allAssets).thenReturn([testAsset1, testAsset2]);
+
+      expect(<String>{"002"}, container.read(testFavoritesProvider));
+
+      container.read(testFavoritesProvider.notifier).toggleFavorite(testAsset2);
+      expect(<String>{}, container.read(testFavoritesProvider));
+
+      container.read(testFavoritesProvider.notifier).toggleFavorite(testAsset1);
+      expect(<String>{"001"}, container.read(testFavoritesProvider));
+    });
+
+    test("Add favorites", () {
+      when(assetNotifier.toggleFavorite(null, false))
+          .thenAnswer((_) async => false);
+
+      when(assetsState.allAssets).thenReturn([]);
+
+      expect(<String>{}, container.read(testFavoritesProvider));
+
+      container.read(testFavoritesProvider.notifier).addToFavorites(
+        [
+          _getTestAsset("001", false),
+          _getTestAsset("002", false),
+        ],
+      );
+
+      expect(<String>{"001", "002"}, container.read(testFavoritesProvider));
+    });
+  });
+}