I notice this issue when using Alchemist to run golden tests in Flutter.
Here is my test code: https://github.com/HevaWu/TestAlchemist
It not shown image in generated goldens, either local or CI folder.
After reading the code, I solve it by adding my own GoldenTestAdapter
The main changes I did is:
// use `home` in pumpWidget
await pumpWidget(
tester,
MaterialApp(
key: rootKey,
theme: theme.stripTextPackages(),
debugShowCheckedModeBanner: false,
supportedLocales: const [Locale('en')],
/// My Changes:
home: DefaultAssetBundle(
bundle: TestAssetBundle(),
child: Material(
type: MaterialType.transparency,
child: Align(
alignment: Alignment.topLeft,
child: ColoredBox(
color: theme.colorScheme.background,
child: Padding(
key: childKey,
padding: const EdgeInsets.all(8),
child: widget,
),
),
),
),
),
),
How I notice this is because: Flutter’s doc mentioned DefaultAssetBundle, and its example is using home there.
Once update to use that, I solve my problem: https://github.com/HevaWu/TestAlchemist/commit/ed93fdcb094425c529f8dda8cabc17977be01cba
Related Reseaching
Try 1: Use precacheImage
/// current workaround for flaky image asset testing.
/// https://github.com/flutter/flutter/issues/38997
Future<void> pump(WidgetTester tester, Widget w) async {
await tester.runAsync(() async {
await tester.pumpWidget(w);
for (var element in find.byType(Image).evaluate()) {
final Image widget = element.widget;
final ImageProvider image = widget.image;
await precacheImage(image, element);
await tester.pumpAndSettle();
}
});
}
Try 2: Add TestAssetBundle
Someone point out this might be issue of loadString() in asset_bundle.dart.
If your AssetManifest.json file exceeds 10kb It will be loaded with isolate that (most likely) will cause your test to finish before assets are loaded so goldens will get empty assets.
One solution — create your own asset bundle and override this method without this size check
class YourOwnTestAssetBundleExtends CachingAssetBundle {
@override
Future<String> loadString(String key, {bool cache = true}) async {
final ByteData data = await load(key);
if (data == null) throw FlutterError('Unable to load asset');
return utf8.decode(data.buffer.asUint8List());
}
@override
Future<ByteData> load(String key) async => rootBundle.load(key);
}
Please refer this doc for more details: https://medium.com/@sardox/flutter-test-and-randomly-missing-assets-in-goldens-ea959cdd336a
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