Unless a user-defined `goldenFileComparator` is set, either manually in a test, or using a `flutter_test_config.dart` file, Android and iOS devices and emulators/simulators have a new default that proxies to the local host filesystem, fixing a long-standing bug (#143299).
- Who is affected
- Applications and packages relying on the previous behaviour or signature. Code that uses FileSystemException.
- Practical impact
- Behaviour or API differences that can break builds or change runtime behaviour.
- What action should I take?
- Follow the official migration guide below, update affected call sites, run `dart fix --apply` where a fix is available, then run your tests.
Official migration guide (excerpt, © The Flutter Authors, CC BY 3.0)
In most cases, we expect users to have to do nothing - this will be in a sense new functionality that replaced functionality that did not work and caused an unhandled exception which would fail a test.
In cases where users wrote custom test infrastructure and comparators, consider
instead removing the [goldenFileComparator][] overrides, and instead rely on
the (new) default which should work as expected:
import 'package:integration_test/integration_test.dart';
- import 'package:my_integration_test/custom_golden_file_comparator.dart';
void main() {
- goldenFileComparator = CustomGoldenFileComparatorThatWorks();
// ...
}Fun fact: The existing code that was used for the web platform was [reused][PR 160484].
AI_PROVIDER (for example to openai-compatible with a local Ollama or LM Studio endpoint) to enable grounded explanations. Everything else on this page works without an AI provider.Listed in the official breaking-changes index (docs.flutter.dev/release/breaking-changes).
An official announcement or migration guide documents an intended behaviour or API change. A verified source change (git diff) shows code changed but does not by itself prove a public API is breaking. AI interpretations are labelled and never used to classify a change.
- Official migration guide
- flutter_test
- goldenFileComparator
- Issue 143299
- Issue 160043
- matchesGoldenFile
- PR 160215
- PR 160484
- Source commit
- b3045439b7c0
- Source last updated
- Oct 21, 2026
- Last synchronized
- Oct 21, 2026
- Publication status
- published
Publication history
- Oct 21, 2026, 8:31 PM: new → published (ingestion) — Backed by an official breaking-change/migration guide.
AI_PROVIDER (for example to openai-compatible with a local Ollama or LM Studio endpoint) to enable grounded explanations. Everything else on this page works without an AI provider.