Flutter Driver crashing when main has async operations

[jamesdixon]

Internal: b/147455985

My app has a few async operations that are initialized in main(). This works fine in my actual application. However, when attempting to run integration tests using Flutter Driver, the tests fail with the following error:

Result (on Emulators):
DriverError: Error in Flutter application: Uncaught extension error while executing tap: 'package:flutter_driver/src/extension/extension.dart': Failed assertion: line 193 pos 14: 'WidgetsBinding.instance.isRootWidgetAttached || !command.requiresRootWidgetAttached': No root widget is attached; have you remembered to call runApp()?

From what I can tell, Flutter Driver doesn't let the app fully initialize before running the tests. If I remove the async operation, things run as expected.

Steps to Reproduce

I've created a minimal reproduction in this repo: https://github.com/jamesdixon/hive_flutter_driver_issue

1. Clone the repo
2. Run flutter drive --target=test_driver/run_app.dart

Logs

The log output was quite long so I pasted it into a gist here: https://gist.github.com/jamesdixon/0b4d0895f6707bdaba439b158eb1110c

No issues found! (ran in 2.3s)

[✓] Flutter (Channel stable, v1.9.1+hotfix.2, on Mac OS X 10.14.5 18F132, locale en-US)
    • Flutter version 1.9.1+hotfix.2 at /Users/jamesdixon/flutter
    • Framework revision 2d2a1ffec9 (2 weeks ago), 2019-09-06 18:39:49 -0700
    • Engine revision b863200c37
    • Dart version 2.5.0

 
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
    • Android SDK at /Users/jamesdixon/Library/Android/sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-28, build-tools 28.0.3
    • ANDROID_HOME = /Users/jamesdixon/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 10.3)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 10.3, Build version 10G8
    • CocoaPods version 1.7.4

[✓] Android Studio (version 3.5)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 38.2.3
    • Dart plugin version 191.8423
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)

[✓] VS Code (version 1.38.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.4.1

[✓] Connected device (1 available)
    • iPhone 7 Plus • 790FC845-4FE6-49C0-8B15-09E3BE74FA3F • ios • com.apple.CoreSimulator.SimRuntime.iOS-12-4 (simulator)

[anjrew]

Also getting this issue

[bgetsug]

Same issue here...my current workaround is to add some sleep():

//...
setUpAll(() async {
    driver = await FlutterDriver.connect();

    await sleep(Duration(seconds: 10));

   // more setup...
}   

[zeucxb]

Same here!

[russell-sf]

Since the call to await in main defers the creation of the app, the flutter driver starts up immediately and starts running tests. Problem is the app may not be fully initialized since the awaited call could still be in flight. That's why adding the delay before running your tests fixes the problem.

Flutter should not start the tests until runApp is actually called.

[jonahwilliams]

To fix this, the driver bindings could be updated to send a handshake single to the command line test. Then FlutterDriver.connect could be updated to wait for this signal before beginning

DriverBinding: https://github.com/flutter/flutter/blob/master/packages/flutter_driver/lib/src/extension/extension.dart#L45

[msmaromi]

Sometimes I got this also

[matejhocevar]

@jonahwilliams can you give more instructions on how to update FlutterDriver.connect in order for Flutter driver to work with async main?

[jonahwilliams]

connect would need to wait for a firstFrame event or similar event from when the Widget tree is attached. I'm not quite sure what the exact approach would be

[bionara]

I can't seem to get mine working - even putting the sleep i get the same error:

[trace] FlutterDriver: Isolate found with number: 420724065357151
[trace] FlutterDriver: Isolate is paused at start.
[trace] FlutterDriver: Attempting to resume isolate
[trace] FlutterDriver: Waiting for service extension
[warning] FlutterDriver: Flutter Driver extension is taking a long time to become available. Ensure your test app (often "lib/main.dart") imports "package:flutter_driver/driver_extension.dart" and calls enableFlutterDriverExtension() as the first call in main().

I tried the enableFlutterDriverExtension in main, but that didn't do anything; furthermore, this actually stopped it working on my teammate's machine!