created the repository implementation in the data layer with test dri…

…ven development (news feed feature)

lib/core/error/exceptions.dart

@@ -0,0 +1,3 @@
+class ServerException implements Exception {}
+
+class ConnectivityException implements Exception {}

lib/core/error/failures.dart

@@ -11,3 +11,8 @@ abstract class Failure extends Equatable {
     return properties != null ? [properties] : [];
   }
 }
+
+// concrete failure classes that map exceptions 1 to 1
+class ServerFailure extends Failure {}
+
+class ConnectivityFailure extends Failure {}

lib/core/platform/network_info.dart

@@ -0,0 +1,3 @@
+abstract class NetworkInfo {
+  Future<bool> checkConnection();
+}

lib/features/news_feed/data/data_sources/news_feed_remote_data_source.dart

@@ -0,0 +1,5 @@
+import 'package:news_app/features/news_feed/data/models/news_feed_model.dart';
+
+abstract class NewsFeedRemoteDataSource {
+  Future<NewsFeedModel> getNewsFeedForCategory(String category);
+}

lib/features/news_feed/data/repositories/news_feed_repository_impl.dart

@@ -0,0 +1,31 @@
+import 'package:dartz/dartz.dart';
+import 'package:news_app/core/error/exceptions.dart';
+import 'package:news_app/core/error/failures.dart';
+import 'package:news_app/core/platform/network_info.dart';
+import 'package:news_app/features/news_feed/data/data_sources/news_feed_remote_data_source.dart';
+import 'package:news_app/features/news_feed/domain/entities/news_feed_entity.dart';
+import 'package:news_app/features/news_feed/domain/repositories/news_feed_repository.dart';
+
+class NewsFeedRepositoryImpl extends NewsFeedRepository {
+  final NetworkInfo networkInfo;
+  final NewsFeedRemoteDataSource remoteDataSource;
+
+  NewsFeedRepositoryImpl(
+      {required this.networkInfo, required this.remoteDataSource});
+
+  @override
+  Future<Either<Failure, NewsFeedEntity>> getNewsFeed(String category) async {
+    try {
+      await networkInfo.checkConnection();
+      final NewsFeedEntity remoteTrivia =
+          await remoteDataSource.getNewsFeedForCategory(category);
+      // can also cache the data when the remote fetch is successful
+      // and return the cached value if there is no network connection
+      return Right(remoteTrivia);
+    } on ConnectivityException {
+      return Left(ConnectivityFailure());
+    } on ServerException {
+      return Left(ServerFailure());
+    }
+  }
+}

test/features/news_feed/data/repositories/news_feed_repository_impl_test.dart

@@ -0,0 +1,128 @@
+import 'package:dartz/dartz.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mockito/annotations.dart';
+import 'package:mockito/mockito.dart';
+import 'package:news_app/core/error/exceptions.dart';
+import 'package:news_app/core/error/failures.dart';
+import 'package:news_app/core/platform/network_info.dart';
+import 'package:news_app/features/news_feed/data/data_sources/news_feed_remote_data_source.dart';
+import 'package:news_app/features/news_feed/data/models/news_feed_model.dart';
+import 'package:news_app/features/news_feed/data/repositories/news_feed_repository_impl.dart';
+import 'package:news_app/features/news_feed/domain/entities/news_feed_entity.dart';
+
+import '../../../../core/fixtures/api_configs.dart';
+import 'news_feed_repository_impl_test.mocks.dart';
+
+//mock the abstract network info (core/platform)
+@GenerateNiceMocks([MockSpec<NetworkInfo>()])
+//mock the abstract remote data source
+@GenerateNiceMocks([MockSpec<NewsFeedRemoteDataSource>()])
+void main() {
+  late MockNetworkInfo mockNetworkInfo;
+  late MockNewsFeedRemoteDataSource mockNewsFeedRemoteDataSource;
+  late NewsFeedRepositoryImpl repositoryImpl;
+
+  setUp(() {
+    mockNetworkInfo = MockNetworkInfo();
+    mockNewsFeedRemoteDataSource = MockNewsFeedRemoteDataSource();
+    repositoryImpl = NewsFeedRepositoryImpl(
+      remoteDataSource: mockNewsFeedRemoteDataSource,
+      networkInfo: mockNetworkInfo,
+    );
+  });
+
+  const testCategory = kNewsAPICategoryTechnology;
+  const testNewsFeedModel = NewsFeedModel(
+    status: "ok",
+    totalResults: 1,
+    articles: [
+      ArticlesModel(
+        source: SourceModel(
+          name: "Nintendo Life",
+        ),
+        author: "Liam Doolan",
+        title:
+            "Metal Gear Solid: Master Collection Vol. 1 Resolution & Frame Rate Chart Released - Nintendo Life",
+        description: "Here's how the Switch version compares",
+        url:
+            "https://www.nintendolife.com/news/2023/09/metal-gear-solid-master-collection-vol-1-resolution-and-frame-rate-chart-released",
+        urlToImage:
+            "https://images.nintendolife.com/9ae5106942e8a/1280x720.jpg",
+        publishedAt: "2023-09-24T05:35:00Z",
+        content:
+            "Image: Konami\r\nHideo Kojima's legendary series Metal Gear Solid returns as a collection release this October on all platforms including the Nintendo Switch, and as part of this Konami has now shared … [+1295 chars]",
+      )
+    ],
+  );
+  const NewsFeedEntity testNewsFeedEntity = testNewsFeedModel;
+
+  group("getNewsFeed tests", () {
+    test('should check if the device is online', () async {
+      //arrange
+      when(mockNetworkInfo.checkConnection()).thenAnswer((_) async => true);
+      // act
+      await repositoryImpl.getNewsFeed(testCategory);
+      // assert
+      verify(mockNetworkInfo.checkConnection());
+    });
+
+    group("device is online", () {
+      setUp(() async {
+        //always return true for this group
+        when(mockNetworkInfo.checkConnection()).thenAnswer((_) async => true);
+      });
+
+      test(
+        'should return remote data when the call to remote data source is successful',
+        () async {
+          // arrange
+          when(mockNewsFeedRemoteDataSource
+                  .getNewsFeedForCategory(testCategory))
+              .thenAnswer((_) async => testNewsFeedModel);
+          // act
+          final result = await repositoryImpl.getNewsFeed(testCategory);
+          // assert
+          verify(mockNewsFeedRemoteDataSource
+              .getNewsFeedForCategory(testCategory));
+          expect(result, equals(const Right(testNewsFeedEntity)));
+        },
+      );
+
+      test(
+        'should return ServerFailure when the call to remote data source is unsuccessful',
+        () async {
+          // arrange
+          when(mockNewsFeedRemoteDataSource
+                  .getNewsFeedForCategory(testCategory))
+              .thenThrow(ServerException());
+          // act
+          final result = await repositoryImpl.getNewsFeed(testCategory);
+          // assert
+          verify(mockNewsFeedRemoteDataSource
+              .getNewsFeedForCategory(testCategory));
+          expect(result, equals(Left(ServerFailure())));
+        },
+      );
+    });
+
+    group("device is offline", () {
+      setUp(() async {
+        //always return false for this group
+        when(mockNetworkInfo.checkConnection())
+            .thenThrow(ConnectivityException());
+      });
+
+      test(
+          "should return Connectivity Failure when there is no internet connection",
+          () async {
+        //arrange
+
+        //act
+        final result = await repositoryImpl.getNewsFeed(testCategory);
+        //assert
+        verifyZeroInteractions(mockNewsFeedRemoteDataSource);
+        expect(result, Left(ConnectivityFailure()));
+      });
+    });
+  });
+}

test/features/news_feed/data/repositories/news_feed_repository_impl_test.mocks.dart

@@ -0,0 +1,79 @@
+// Mocks generated by Mockito 5.4.2 from annotations
+// in news_app/test/features/news_feed/data/repositories/news_feed_repository_impl_test.dart.
+// Do not manually edit this file.
+
+// ignore_for_file: no_leading_underscores_for_library_prefixes
+import 'dart:async' as _i4;
+
+import 'package:mockito/mockito.dart' as _i1;
+import 'package:news_app/core/platform/network_info.dart' as _i3;
+import 'package:news_app/features/news_feed/data/data_sources/news_feed_remote_data_source.dart'
+    as _i5;
+import 'package:news_app/features/news_feed/data/models/news_feed_model.dart'
+    as _i2;
+
+// ignore_for_file: type=lint
+// ignore_for_file: avoid_redundant_argument_values
+// ignore_for_file: avoid_setters_without_getters
+// ignore_for_file: comment_references
+// ignore_for_file: implementation_imports
+// ignore_for_file: invalid_use_of_visible_for_testing_member
+// ignore_for_file: prefer_const_constructors
+// ignore_for_file: unnecessary_parenthesis
+// ignore_for_file: camel_case_types
+// ignore_for_file: subtype_of_sealed_class
+
+class _FakeNewsFeedModel_0 extends _i1.SmartFake implements _i2.NewsFeedModel {
+  _FakeNewsFeedModel_0(
+    Object parent,
+    Invocation parentInvocation,
+  ) : super(
+          parent,
+          parentInvocation,
+        );
+}
+
+/// A class which mocks [NetworkInfo].
+///
+/// See the documentation for Mockito's code generation for more information.
+class MockNetworkInfo extends _i1.Mock implements _i3.NetworkInfo {
+  @override
+  _i4.Future<bool> checkConnection() => (super.noSuchMethod(
+        Invocation.method(
+          #checkConnection,
+          [],
+        ),
+        returnValue: _i4.Future<bool>.value(false),
+        returnValueForMissingStub: _i4.Future<bool>.value(false),
+      ) as _i4.Future<bool>);
+}
+
+/// A class which mocks [NewsFeedRemoteDataSource].
+///
+/// See the documentation for Mockito's code generation for more information.
+class MockNewsFeedRemoteDataSource extends _i1.Mock
+    implements _i5.NewsFeedRemoteDataSource {
+  @override
+  _i4.Future<_i2.NewsFeedModel> getNewsFeedForCategory(String? category) =>
+      (super.noSuchMethod(
+        Invocation.method(
+          #getNewsFeedForCategory,
+          [category],
+        ),
+        returnValue: _i4.Future<_i2.NewsFeedModel>.value(_FakeNewsFeedModel_0(
+          this,
+          Invocation.method(
+            #getNewsFeedForCategory,
+            [category],
+          ),
+        )),
+        returnValueForMissingStub:
+            _i4.Future<_i2.NewsFeedModel>.value(_FakeNewsFeedModel_0(
+          this,
+          Invocation.method(
+            #getNewsFeedForCategory,
+            [category],
+          ),
+        )),
+      ) as _i4.Future<_i2.NewsFeedModel>);
+}