Not sure if it's a limitation or something, but below code does not load anything. I have some data driven behaviour that I'd like to test isolated. class Loader import 'dart:async'; import 'package:flutter/services.dart' show rootBundle; class Loader { Future<String> load() async{ return await rootBundle.loadString('assets/json/sketch.json'); } } The test testWidgets('Should parse load sketch.json', (WidgetTester tester) async { var loaderFuture = new Loader(); Future<String> resultFuture = loaderFuture.load(); resultFuture.then((value) => print(value)) .catchError((error) => print(error)); while(true){}; }); Future does not return neither success nor error and hangs forever. I know the while(true) locking up the test, but for now I just wanted to see sketch.json printed Asset location Continue reading...