golden_test_cached_network_image

CachedNetworkImage support for golden_test.

The problem

CachedNetworkImage doesn't paint through NetworkImage. It fetches through flutter_cache_manager, whose persistence layer needs SQLite and path_provider, and neither works inside Flutter's fake-async test zone.

The result isn't a failure you can read. A CachedNetworkImage in a golden test hangs — the run stalls until it times out as did not complete, with nothing in the output naming the widget, the URL, or the cache.

The fix

This package swaps in a cache manager that keeps every file in memory, so reads complete as a microtask and settle inside the normal pumpAndSettle loop. It serves the same placeholder golden_test uses for Image.network, so every image in a golden renders identically regardless of which widget loaded it.

It ships separately from golden_test because the fix requires depending on cached_network_image and flutter_cache_manager. Keeping it here means projects that don't use CachedNetworkImage never resolve either.

Setup

dev_dependencies:
  golden_test: ^2.0.0
  golden_test_cached_network_image: ^1.0.0

// test/flutter_test_config.dart
import 'dart:async';

import 'package:golden_test_cached_network_image/golden_test_cached_network_image.dart';

Future<void> testExecutable(FutureOr<void> Function() testMain) async {
  // ... your other golden_test configuration ...
  setupGoldenTestCachedNetworkImage();
  return testMain();
}

That's it. Every CachedNetworkImage in a golden test now resolves to the same placeholder golden_test serves for Image.network, so both render identically.

Custom cache manager

Pass a builder to substitute your own manager — to serve different bytes per URL, to assert on what was requested, or to wrap a project-specific subclass:

setupGoldenTestCachedNetworkImage(
  cacheManagerBuilder: () => MyGoldenCacheManager(),
);

It's a builder rather than an instance because it runs once per test, so each test gets a fresh manager and cache state can't leak between them. Whatever it returns must avoid SQLite and path_provider — that's the whole reason the default exists.

What the default manager does

GoldenTestCacheManager keeps every "file" in an in-memory filesystem, so reads complete as a microtask and settle inside the normal pumpAndSettle loop.

  • Entries are addressed by cache key, so CachedNetworkImage(cacheKey: ...) works and FileInfo.originalUrl still reports the URL. Without an explicit key the URL doubles as the key, as in the real cache manager.
  • getFileStream emits a single FileInfo and never a DownloadProgress, so progressIndicatorBuilder never runs — progress fractions would make goldens depend on download timing. Use placeholder to golden the pre-load state.
  • The bytes come from goldenTestNetworkImageStubPng, so overriding that in golden_test changes this package's output too.

Caveat

setupGoldenTestCachedNetworkImage sets CachedNetworkImageProvider.defaultCacheManager, so it reaches widgets that use the default. A CachedNetworkImage built with an explicit cacheManager: keeps the one you gave it, and behaves as it would without this package — including hanging the test if that manager is the real one. Pass your test manager to those widgets too.

License

BSD 3-Clause.

Libraries

golden_test_cached_network_image
CachedNetworkImage support for golden_test.