Creating test cases for RestClient

lib/data/network/rest_client.dart

@@ -6,13 +6,18 @@ import 'package:http/http.dart' as http;
 import 'exceptions/network_exceptions.dart';
 
 class RestClient {
+  http.Client _client;
+
+  RestClient({http.Client client}) {
+    _client = client ?? http.Client();
+  }
 
   // instantiate json decoder for json serialization
   final JsonDecoder _decoder = JsonDecoder();
 
   // Get:-----------------------------------------------------------------------
   Future<dynamic> get(String url) {
-    return http.get(url).then((http.Response response) {
+    return _client.get(url).then((http.Response response) {
       final String res = response.body;
       final int statusCode = response.statusCode;
 
@@ -28,7 +33,7 @@ class RestClient {
 
   // Post:----------------------------------------------------------------------
   Future<dynamic> post(String url, {Map headers, body, encoding}) {
-    return http
+    return _client
         .post(url, body: body, headers: headers, encoding: encoding)
         .then((http.Response response) {
       final String res = response.body;

pubspec.yaml

@@ -85,6 +85,7 @@ dev_dependencies:
       url: https://github.com/google/inject.dart.git
       path: package/inject_generator
       ref: 7c3cbf6
+  mockito: ^4.1.1
 
 flutter_icons:
   image_path: "assets/icons/ic_launcher.png"

test/data/network/rest_client_mock_test.dart

@@ -0,0 +1,61 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mockito/mockito.dart';
+import 'package:http/http.dart' as http;
+
+import '../../../lib/data/network/exceptions/network_exceptions.dart';
+import '../../../lib/data/network/rest_client.dart';
+
+// Create a MockClient using the Mock class provided by the Mockito package.
+// Create new instances of this class in each test.
+class MockClient extends Mock implements http.Client {}
+
+main() {
+  group('RestClient', () {
+    group('get', () {
+      test('returns a Map if the http call completes successfully', () async {
+        // Arrange
+        final mockitoClient = MockClient();
+        final url = 'https://example.com';
+
+        // Act
+        // Use Mockito to return a successful response when it calls the
+        // provided http.Client.
+        when(mockitoClient.get(url))
+            .thenAnswer((_) async => http.Response('{"name": "Jorge"}', 200));
+
+        final restClient = RestClient(client: mockitoClient);
+        final response = await restClient.get(url);
+
+        // Assert
+        // response should be a map
+        if (!(response is Map)) fail('response should be a map');
+      });
+
+      test(
+          'throws a network exception if the http call completes with an error',
+          () async {
+        // Arrange
+        final mockitoClient = MockClient();
+        final url = 'https://example.com';
+        dynamic error;
+
+        // Act
+        // Use Mockito to return an unsuccessful response when it calls the
+        // provided http.Client.
+        when(mockitoClient.get(url))
+            .thenAnswer((_) async => http.Response('Not Found', 404));
+
+        final restClient = RestClient(client: mockitoClient);
+        try {
+          await restClient.get(url);
+        } catch (e) {
+          error = e;
+        }
+
+        // Assert
+        if (!(error is NetworkException))
+          fail("didn't throw network exception");
+      });
+    });
+  });
+}