Add a shared preferences test and explain how to test (flutter#96)

packages/shared_preferences/CHANGELOG.md

@@ -1,3 +1,9 @@
+## [0.2.3+1] - 2017-06-04
+
+* Added setMockInitialValues
+* Added a test
+* Updated README
+
 ## [0.2.3] - 2017-06-02
 
 * Suppress warning about unchecked operations when compiling for Android

packages/shared_preferences/README.md

@@ -36,3 +36,16 @@ _incrementCounter() async {
 }
 ```
 
+### Testing
+
+You can populate `SharedPreferences` with initial values in your tests by running this code:
+
+```
+const MethodChannel('plugins.flutter.io/shared_preferences')
+  .setMockMethodCallHandler((MethodCall methodCall) async {
+    if (methodCall.method == 'getAll') {
+      return <String, dynamic>{}; // set initial values here if desired
+    }
+    return null;
+  });
+```

packages/shared_preferences/lib/shared_preferences.dart

@@ -5,6 +5,7 @@
 import 'dart:async';
 
 import 'package:flutter/services.dart';
+import 'package:meta/meta.dart';
 
 const MethodChannel _kChannel =
     const MethodChannel('plugins.flutter.io/shared_preferences');
@@ -103,4 +104,15 @@ class SharedPreferences {
     _preferenceCache.clear();
     return await _kChannel.invokeMethod('clear');
   }
+
+  /// Initializes the shared preferences with mock values for testing.
+  @visibleForTesting
+  static void setMockInitialValues(Map<String, dynamic> values) {
+    _kChannel.setMockMethodCallHandler((MethodCall methodCall) async {
+      if (methodCall.method == 'getAll') {
+        return values;
+      }
+      return null;
+    });
+  }
 }

packages/shared_preferences/pubspec.yaml

@@ -1,6 +1,6 @@
 name: shared_preferences
 
-version: 0.2.3
+version: 0.2.4
 description: A Flutter plugin for reading and writing simple key-value pairs.
 author: Flutter Team <flutter-dev@googlegroups.com>
 homepage: https://github.com/flutter/plugins/tree/master/packages/shared_preferences
@@ -11,8 +11,13 @@ flutter:
     pluginClass: SharedPreferencesPlugin
 
 dependencies:
+  meta: ^1.0.4
   flutter:
     sdk: flutter
 
+dev_dependencies:
+  mockito: ^2.0.2
+  test: ^0.12.20
+
 environment:
     sdk: ">=1.8.0 <2.0.0"

packages/shared_preferences/test/shared_preferences_test.dart

@@ -0,0 +1,115 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:mockito/mockito.dart';
+import 'package:test/test.dart';
+
+import 'package:flutter/services.dart';
+
+import 'package:shared_preferences/shared_preferences.dart';
+
+void main() {
+  group('$SharedPreferences', ()
+  {
+    const MethodChannel channel = const MethodChannel(
+      'plugins.flutter.io/shared_preferences',
+    );
+
+    const kTestValues = const <String, dynamic>{
+      'flutter.String': 'hello world',
+      'flutter.bool': true,
+      'flutter.int': 42,
+      'flutter.double': 3.14159,
+      'flutter.List': const <String>['foo', 'bar'],
+    };
+
+    const kTestValues2 = const <String, dynamic>{
+      'flutter.String': 'goodbye world',
+      'flutter.bool': false,
+      'flutter.int': 1337,
+      'flutter.double': 2.71828,
+      'flutter.List': const <String>['baz', 'quox'],
+    };
+
+    final List<MethodCall> log = <MethodCall>[];
+    SharedPreferences sharedPreferences;
+
+    setUp(() async {
+      channel.setMockMethodCallHandler((MethodCall methodCall) async {
+        log.add(methodCall);
+        if (methodCall.method == 'getAll') {
+          return kTestValues;
+        }
+        return null;
+      });
+      sharedPreferences = await SharedPreferences.getInstance();
+      log.clear();
+    });
+
+    test('reading', () async {
+      expect(sharedPreferences.getString('String'), kTestValues['flutter.String']);
+      expect(sharedPreferences.getBool('bool'), kTestValues['flutter.bool']);
+      expect(sharedPreferences.getInt('int'), kTestValues['flutter.int']);
+      expect(sharedPreferences.getDouble('double'), kTestValues['flutter.double']);
+      expect(sharedPreferences.getStringList('List'), kTestValues['flutter.List']);
+      expect(log, equals([]));
+    });
+
+    test('writing', () async {
+      sharedPreferences.setString('String', kTestValues2['flutter.String']);
+      sharedPreferences.setBool('bool', kTestValues2['flutter.bool']);
+      sharedPreferences.setInt('int', kTestValues2['flutter.int']);
+      sharedPreferences.setDouble('double', kTestValues2['flutter.double']);
+      sharedPreferences.setStringList('List', kTestValues2['flutter.List']);
+      expect(sharedPreferences.getString('String'), kTestValues2['flutter.String']);
+      expect(sharedPreferences.getBool('bool'), kTestValues2['flutter.bool']);
+      expect(sharedPreferences.getInt('int'), kTestValues2['flutter.int']);
+      expect(sharedPreferences.getDouble('double'), kTestValues2['flutter.double']);
+      expect(sharedPreferences.getStringList('List'), kTestValues2['flutter.List']);
+      expect(log, equals([]));
+      await sharedPreferences.commit();
+      expect(log, equals(<MethodCall>[
+        new MethodCall(
+          'setString',
+          { 'key': 'flutter.String', 'value': kTestValues2['flutter.String'] }
+        ),
+        new MethodCall(
+          'setBool',
+          { 'key': 'flutter.bool', 'value': kTestValues2['flutter.bool'] }
+        ),
+        new MethodCall(
+          'setInt',
+          { 'key': 'flutter.int', 'value': kTestValues2['flutter.int'] }
+        ),
+        new MethodCall(
+          'setDouble',
+          { 'key': 'flutter.double', 'value': kTestValues2['flutter.double'] }
+        ),
+        new MethodCall(
+          'setStringList',
+          { 'key': 'flutter.List', 'value': kTestValues2['flutter.List'] }
+        ),
+        new MethodCall('commit'),
+      ]));
+    });
+
+    test('clearing', () async {
+      await sharedPreferences.clear();
+      expect(sharedPreferences.getString('String'), null);
+      expect(sharedPreferences.getBool('bool'), null);
+      expect(sharedPreferences.getInt('int'), null);
+      expect(sharedPreferences.getDouble('double'), null);
+      expect(sharedPreferences.getStringList('List'), null);
+      expect(log, equals(<MethodCall>[new MethodCall('clear')]));
+    });
+
+    test('mocking', () async {
+      expect(await channel.invokeMethod('getAll'), kTestValues);
+      SharedPreferences.setMockInitialValues(kTestValues2);
+      expect(await channel.invokeMethod('getAll'), kTestValues2);
+    });
+  });
+}
+
+class MockPlatformChannel extends Mock implements MethodChannel { }