Fix bug and tests

Author: renefloor

flutter_cache_manager/lib/src/cache_managers/image_cache_manager.dart

@@ -133,12 +133,16 @@ mixin ImageCacheManager on BaseCacheManager {
   }
 }
 
-Future<ui.Image> _decodeImage(File file, {int? width, int? height, bool allowUpscaling = false}) {
-  // since we set allowUpscaling to false, the width and height parameters are actually max-width.
-  final image = ResizeImage(FileImage(file), width: width, height: height, allowUpscaling: allowUpscaling);
+Future<ui.Image> _decodeImage(File file,
+    {int? width, int? height, bool allowUpscaling = false}) {
+  var shouldResize = width != null || height != null;
+  var fileImage = FileImage(file);
+  final image = shouldResize
+      ? ResizeImage(fileImage,
+          width: width, height: height, allowUpscaling: allowUpscaling)
+      : fileImage as ImageProvider;
   final completer = Completer<ui.Image>();
-  image
-      .resolve(const ImageConfiguration())
-      .addListener(ImageStreamListener((info, _) => completer.complete(info.image)));
+  image.resolve(const ImageConfiguration()).addListener(
+      ImageStreamListener((info, _) => completer.complete(info.image)));
   return completer.future;
 }

flutter_cache_manager/test/image_cache_manager_test.dart

@@ -2,6 +2,7 @@ import 'dart:io' as io;
 import 'dart:typed_data';
 import 'dart:ui';
 
+import 'package:flutter/material.dart';
 import 'package:flutter_cache_manager/flutter_cache_manager.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'cache_manager_test.dart';
@@ -13,6 +14,17 @@ const fileName = 'test.jpg';
 const fileUrl = 'baseflow.com/test';
 final validTill = DateTime.now().add(const Duration(days: 1));
 void main() {
+
+  setUp(() {
+    WidgetsFlutterBinding.ensureInitialized();
+  });
+
+  tearDown(() {
+    PaintingBinding.instance?.imageCache?.clear();
+    PaintingBinding.instance?.imageCache?.clearLiveImages();
+  });
+
+
   group('Test image resizing', () {
     test('Test original image size', () async {
       final bytes = await getExampleImage();