packages/flutter/test/foundation/capture_output.dart

// 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:async';
import 'package:flutter/foundation.dart';

List<String> captureOutput(VoidCallback fn) {
  final log = <String>[];

  runZoned<void>(
    fn,
    zoneSpecification: ZoneSpecification(
      print: (Zone self, ZoneDelegate parent, Zone zone, String line) {
        log.add(line);
      },
    ),
  );

  return log;
}