[image_picker] Switch unit tests to mock plaform implementation (#5706)

`image_picker`'s app-facing tests were never updated during federation to
use a mock platform implementation, and instead were still mocking method
channels. That makes them fragile to implementation details of the
default method channel implementation that is part of another package,
and thus subject to breakage when the method channel changes.

This converts them to using a mock platform implementation, so it's only
testing the layer within this package.

Removes some tests that were testing things that only made sense at the
method channel layer.

Adds argument assertions that there were tests for, but were previously
only enforced in the implementations. As these are API constraints, they
should be enforced at the API layer, not at each implementation's layer
as they currently are.

packages/image_picker/image_picker/CHANGELOG.md

@@ -1,3 +1,10 @@
+## 0.8.5+3
+
+* Adds argument error assertions to the app-facing package, to ensure
+  consistency across platform implementations.
+* Updates tests to use a mock platform instead of relying on default
+  method channel implementation internals.
+
 ## 0.8.5+2
 
 * Minor fixes for new analysis options.

packages/image_picker/image_picker/lib/image_picker.dart

@@ -207,6 +207,17 @@ class ImagePicker {
     int? imageQuality,
     CameraDevice preferredCameraDevice = CameraDevice.rear,
   }) {
+    if (imageQuality != null && (imageQuality < 0 || imageQuality > 100)) {
+      throw ArgumentError.value(
+          imageQuality, 'imageQuality', 'must be between 0 and 100');
+    }
+    if (maxWidth != null && maxWidth < 0) {
+      throw ArgumentError.value(maxWidth, 'maxWidth', 'cannot be negative');
+    }
+    if (maxHeight != null && maxHeight < 0) {
+      throw ArgumentError.value(maxHeight, 'maxHeight', 'cannot be negative');
+    }
+
     return platform.getImage(
       source: source,
       maxWidth: maxWidth,
@@ -245,6 +256,17 @@ class ImagePicker {
     double? maxHeight,
     int? imageQuality,
   }) {
+    if (imageQuality != null && (imageQuality < 0 || imageQuality > 100)) {
+      throw ArgumentError.value(
+          imageQuality, 'imageQuality', 'must be between 0 and 100');
+    }
+    if (maxWidth != null && maxWidth < 0) {
+      throw ArgumentError.value(maxWidth, 'maxWidth', 'cannot be negative');
+    }
+    if (maxHeight != null && maxHeight < 0) {
+      throw ArgumentError.value(maxHeight, 'maxHeight', 'cannot be negative');
+    }
+
     return platform.getMultiImage(
       maxWidth: maxWidth,
       maxHeight: maxHeight,

packages/image_picker/image_picker/pubspec.yaml

@@ -3,7 +3,7 @@ description: Flutter plugin for selecting images from the Android and iOS image
   library, and taking new pictures with the camera.
 repository: https://github.com/flutter/plugins/tree/main/packages/image_picker/image_picker
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+image_picker%22
-version: 0.8.5+2
+version: 0.8.5+3
 
 environment:
   sdk: ">=2.14.0 <3.0.0"
@@ -28,6 +28,8 @@ dependencies:
   image_picker_platform_interface: ^2.3.0
 
 dev_dependencies:
+  build_runner: ^2.1.10
+  cross_file: ^0.3.1+1 # Mockito generates a direct include.
   flutter_test:
     sdk: flutter
   mockito: ^5.0.0