[Camera] Made CameraController.isDisposed publicly accessible. Added unit Tests for the new implementation.

packages/camera/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.5.8+15
+
+* Added the `debugCheckIsDisposed` method which can be used in debug mode to validate if the `CameraController` class has been disposed.
+
 ## 0.5.8+14
 
 * Changed the order of the setters for `mediaRecorder` in `MediaRecorderBuilder.java` to make it more readable.

packages/camera/lib/camera.dart

@@ -307,6 +307,13 @@ class CameraController extends ValueNotifier<CameraValue> {
   StreamSubscription<dynamic> _imageStreamSubscription;
   Completer<void> _creatingCompleter;
 
+  /// Checks whether [CameraController.dispose] has completed successfully.
+  ///
+  /// This is a no-op when asserts are disabled.
+  void debugCheckIsDisposed() {
+    assert(_isDisposed);
+  }
+
   /// Initializes the camera on the device.
   ///
   /// Throws a [CameraException] if the initialization fails.

packages/camera/pubspec.yaml

@@ -2,7 +2,7 @@ name: camera
 description: A Flutter plugin for getting information about and controlling the
   camera on Android and iOS. Supports previewing the camera feed, capturing images, capturing video,
   and streaming image buffers to dart.
-version: 0.5.8+14
+version: 0.5.8+15
 homepage: https://github.com/flutter/plugins/tree/master/packages/camera
 
 dependencies:

packages/camera/test/camera_test.dart

@@ -0,0 +1,44 @@
+// 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:camera/camera.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('camera', () {
+    test('debugCheckIsDisposed should not throw assertion error when disposed',
+        () {
+      final MockCameraDescription description = MockCameraDescription();
+      final CameraController controller = CameraController(
+        description,
+        ResolutionPreset.low,
+      );
+
+      controller.dispose();
+
+      expect(controller.debugCheckIsDisposed, returnsNormally);
+    });
+
+    test('debugCheckIsDisposed should throw assertion error when not disposed',
+        () {
+      final MockCameraDescription description = MockCameraDescription();
+      final CameraController controller = CameraController(
+        description,
+        ResolutionPreset.low,
+      );
+
+      expect(
+        () => controller.debugCheckIsDisposed(),
+        throwsAssertionError,
+      );
+    });
+  });
+}
+
+class MockCameraDescription extends CameraDescription {
+  @override
+  CameraLensDirection get lensDirection => CameraLensDirection.back;
+
+  @override
+  String get name => 'back';
+}