DRY up FakeCodec (#149381)

- dedupe the same class in two places
- renamed it to not clash with `FakeCodec` defined somewhere else

packages/flutter/test/painting/image_provider_network_image_test.dart

@@ -5,7 +5,7 @@
 import 'dart:async';
 import 'dart:io';
 import 'dart:math' as math;
-import 'dart:ui' show Codec, FrameInfo, ImmutableBuffer;
+import 'dart:ui' show Codec, ImmutableBuffer;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
@@ -13,6 +13,7 @@ import 'package:flutter_test/flutter_test.dart';
 
 import '../image_data.dart';
 import '../rendering/rendering_tester.dart';
+import 'noop_codec.dart';
 
 void main() {
   TestRenderingFlutterBinding.ensureInitialized();
@@ -227,10 +228,6 @@ void main() {
     debugNetworkImageHttpClientProvider = null;
   }, skip: isBrowser); // [intended] Browser does not resolve images this way.
 
-  Future<Codec> decoder(ImmutableBuffer buffer, {int? cacheWidth, int? cacheHeight, bool? allowUpscaling}) async {
-    return FakeCodec();
-  }
-
   test('Network image sets tag', () async {
     const String url = 'http://test.png';
     const int chunkSize = 8;
@@ -245,7 +242,7 @@ void main() {
 
     const NetworkImage provider = NetworkImage(url);
 
-    final MultiFrameImageStreamCompleter completer = provider.loadBuffer(provider, decoder) as MultiFrameImageStreamCompleter;
+    final MultiFrameImageStreamCompleter completer = provider.loadBuffer(provider, noopCodec) as MultiFrameImageStreamCompleter;
 
     expect(completer.debugLabel, url);
   });
@@ -319,19 +316,3 @@ class _FakeHttpClientResponse extends Fake implements HttpClientResponse {
     return futureValue ?? futureValue as E; // Mirrors the implementation in Stream.
   }
 }
-
-class FakeCodec implements Codec {
-  @override
-  void dispose() {}
-
-  @override
-  int get frameCount => throw UnimplementedError();
-
-  @override
-  Future<FrameInfo> getNextFrame() {
-    throw UnimplementedError();
-  }
-
-  @override
-  int get repetitionCount => throw UnimplementedError();
-}

packages/flutter/test/painting/image_provider_test.dart

@@ -15,6 +15,7 @@ import 'package:flutter_test/flutter_test.dart';
 import '../image_data.dart';
 import '../rendering/rendering_tester.dart';
 import 'mocks_for_image_cache.dart';
+import 'noop_codec.dart';
 
 void main() {
   TestRenderingFlutterBinding.ensureInitialized();
@@ -88,22 +89,18 @@ void main() {
     final FileImage provider = FileImage(file);
 
     expect(provider.loadBuffer(provider, (ImmutableBuffer buffer, {int? cacheWidth, int? cacheHeight, bool? allowUpscaling}) async {
-      return Future<Codec>.value(FakeCodec());
+      return Future<Codec>.value(NoopCodec());
     }), isA<MultiFrameImageStreamCompleter>());
 
     expect(await error.future, isStateError);
   });
 
-  Future<Codec> decoder(ImmutableBuffer buffer, {int? cacheWidth, int? cacheHeight, bool? allowUpscaling}) async {
-    return FakeCodec();
-  }
-
   test('File image sets tag', () async {
     final MemoryFileSystem fs = MemoryFileSystem();
     final File file = fs.file('/blue.png')..createSync(recursive: true)..writeAsBytesSync(kBlueSquarePng);
     final FileImage provider = FileImage(file);
 
-    final MultiFrameImageStreamCompleter completer = provider.loadBuffer(provider, decoder) as MultiFrameImageStreamCompleter;
+    final MultiFrameImageStreamCompleter completer = provider.loadBuffer(provider, noopCodec) as MultiFrameImageStreamCompleter;
 
     expect(completer.debugLabel, file.path);
   });
@@ -112,7 +109,7 @@ void main() {
     final Uint8List bytes = Uint8List.fromList(kBlueSquarePng);
     final MemoryImage provider = MemoryImage(bytes);
 
-    final MultiFrameImageStreamCompleter completer = provider.loadBuffer(provider, decoder) as MultiFrameImageStreamCompleter;
+    final MultiFrameImageStreamCompleter completer = provider.loadBuffer(provider, noopCodec) as MultiFrameImageStreamCompleter;
 
     expect(completer.debugLabel, 'MemoryImage(${describeIdentity(bytes)})');
   });
@@ -121,7 +118,7 @@ void main() {
     const String asset = 'images/blue.png';
     final ExactAssetImage provider = ExactAssetImage(asset, bundle: _TestAssetBundle());
     final AssetBundleImageKey key = await provider.obtainKey(ImageConfiguration.empty);
-    final MultiFrameImageStreamCompleter completer = provider.loadBuffer(key, decoder) as MultiFrameImageStreamCompleter;
+    final MultiFrameImageStreamCompleter completer = provider.loadBuffer(key, noopCodec) as MultiFrameImageStreamCompleter;
 
     expect(completer.debugLabel, asset);
   });
@@ -131,7 +128,7 @@ void main() {
     final ResizeImage provider = ResizeImage(MemoryImage(bytes), width: 40, height: 40);
     final MultiFrameImageStreamCompleter completer = provider.loadBuffer(
       await provider.obtainKey(ImageConfiguration.empty),
-      decoder,
+      noopCodec,
     ) as MultiFrameImageStreamCompleter;
 
     expect(completer.debugLabel, 'MemoryImage(${describeIdentity(bytes)}) - Resized(40×40)');
@@ -167,22 +164,6 @@ void main() {
   });
 }
 
-class FakeCodec implements Codec {
-  @override
-  void dispose() {}
-
-  @override
-  int get frameCount => throw UnimplementedError();
-
-  @override
-  Future<FrameInfo> getNextFrame() {
-    throw UnimplementedError();
-  }
-
-  @override
-  int get repetitionCount => throw UnimplementedError();
-}
-
 class _TestAssetBundle extends CachingAssetBundle {
   @override
   Future<ByteData> load(String key) async {

packages/flutter/test/painting/noop_codec.dart

@@ -0,0 +1,27 @@
+// Copyright 2014 The Flutter 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 'dart:ui';
+
+class NoopCodec implements Codec {
+  @override
+  void dispose() {}
+
+  @override
+  int get frameCount => throw UnimplementedError();
+
+  @override
+  Future<FrameInfo> getNextFrame() => throw UnimplementedError();
+
+  @override
+  int get repetitionCount => throw UnimplementedError();
+}
+
+Future<Codec> noopCodec(
+  ImmutableBuffer buffer, {
+  int? cacheWidth,
+  int? cacheHeight,
+  bool? allowUpscaling,
+}) async =>
+    NoopCodec();