Added unit tests

Author: Levi-Lesches

pkgs/dartpad_ui/lib/local_storage.dart

@@ -2,17 +2,12 @@
 // for details. 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:web/web.dart' as web;
+import 'local_storage/stub.dart'
+  if (dart.library.js_util) 'local_storage/web.dart';
 
-const _userInputKey = 'user_';
+abstract class LocalStorage {
+  static LocalStorage instance = LocalStorageImpl();
 
-class LocalStorage {
-  static final instance = LocalStorage._();
-
-  LocalStorage._();
-
-  void saveUserCode(String code) =>
-      web.window.localStorage.setItem(_userInputKey, code);
-
-  String? getUserCode() => web.window.localStorage.getItem(_userInputKey);
+  void saveUserCode(String code);
+  String? getUserCode();
 }

pkgs/dartpad_ui/lib/local_storage/stub.dart

@@ -0,0 +1,16 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../local_storage.dart';
+import '../utils.dart';
+
+class LocalStorageImpl extends LocalStorage {
+  String? _code;
+
+  @override
+  void saveUserCode(String code) => _code = code;
+
+  @override
+  String? getUserCode() => _code?.nullIfEmpty;
+}

pkgs/dartpad_ui/lib/local_storage/web.dart

@@ -0,0 +1,20 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. 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:web/web.dart' as web;
+
+import '../local_storage.dart';
+import '../utils.dart';
+
+const _userInputKey = 'user_';
+
+class LocalStorageImpl extends LocalStorage {
+  @override
+  void saveUserCode(String code) =>
+    web.window.localStorage.setItem(_userInputKey, code);
+
+  @override
+  String? getUserCode() =>
+    web.window.localStorage.getItem(_userInputKey)?.nullIfEmpty;
+}

pkgs/dartpad_ui/lib/utils.dart

@@ -184,3 +184,7 @@ enum MessageState {
   showing,
   closing;
 }
+
+extension StringUtils on String {
+  String? get nullIfEmpty => isEmpty ? null : this;
+}

pkgs/dartpad_ui/test/autosave_test.dart

@@ -0,0 +1,91 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:convert';
+
+import 'package:dartpad_ui/gists.dart';
+import 'package:dartpad_ui/local_storage.dart';
+import 'package:dartpad_ui/model.dart';
+import 'package:dartpad_ui/samples.g.dart';
+import 'package:dartpad_ui/utils.dart';
+import 'package:test/test.dart';
+
+import 'gists_test.dart';
+
+String getFallback() =>
+  LocalStorage.instance.getUserCode() ?? Samples.defaultSnippet();
+
+void main() {
+  const channel = Channel.stable;
+  group('Autosave:', () {
+    test('empty content is treated as null', () {
+      expect(''.nullIfEmpty, isNull);
+
+      LocalStorage.instance.saveUserCode('non-empty');
+      expect(LocalStorage.instance.getUserCode(), isNotNull);
+
+      LocalStorage.instance.saveUserCode('');
+      expect(LocalStorage.instance.getUserCode(), isNull);
+    });
+
+    test('null content means sample snippet is shown', () async {
+      final model = AppModel();
+      final services = AppServices(model, channel);
+      LocalStorage.instance.saveUserCode('');
+      expect(LocalStorage.instance.getUserCode(), isNull);
+
+      await services.performInitialLoad(
+        fallbackSnippet: getFallback(),
+      );
+      expect(model.sourceCodeController.text, equals(Samples.defaultSnippet()));
+    });
+
+    test('non-null content is shown', () async {
+      const sample = 'Hello, World!';
+      final model = AppModel();
+      final services = AppServices(model, channel);
+      LocalStorage.instance.saveUserCode(sample);
+      expect(LocalStorage.instance.getUserCode(), equals(sample));
+
+      await services.performInitialLoad(
+        fallbackSnippet: getFallback(),
+      );
+      expect(model.sourceCodeController.text, equals(sample));
+    });
+
+    group('content is not shown with', () {
+      const sample = 'Hello, World!';
+      LocalStorage.instance.saveUserCode(sample);
+      // Not testing flutterSampleId to avoid breaking when the Flutter docs change
+
+      test('Gist', () async {
+        final model = AppModel();
+        final services = AppServices(model, channel);
+        expect(LocalStorage.instance.getUserCode(), equals(sample));
+
+        // From gists_tests.dart
+        const gistId = 'd3bd83918d21b6d5f778bdc69c3d36d6';
+        await services.performInitialLoad(
+          fallbackSnippet: getFallback(),
+          gistId: gistId,
+        );
+        expect(model.sourceCodeController.text, isNot(equals(sample)));
+      });
+
+      test('sample', () async {
+        final model = AppModel();
+        final services = AppServices(model, channel);
+        expect(LocalStorage.instance.getUserCode(), equals(sample));
+
+        // From samples_test.dart
+        const sampleId = 'dart';
+        await services.performInitialLoad(
+          fallbackSnippet: getFallback(),
+          sampleId: sampleId,
+        );
+        expect(model.sourceCodeController.text, isNot(equals(sample)));
+      });
+    });
+  });
+}