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🚨 Error handling

Happy path testing is fantastic, but error scenarios separate amateur from professional testing! Users will inevitably:

  • 📝 Submit empty forms
  • 🔄 Retry failed actions
  • 🚫 Encounter validation errors
  • 😅 Make unexpected inputs

🔑 Keys​

Let's add keys:

lib/app_keys.dart
abstract class AppKeys {
  // previous keys
  static const errorDialog = ValueKey('ErrorDialog');
  static const errorDialogOKButton = ValueKey('ErrorDialogOKButton');
}

... and assign them to widgets:

lib/main.dart
showDialog(
  context: context,
  builder: (context) => AlertDialog(
    key: AppKeys.errorDialog, // 👈 here
    title: Text('No name'),
    content: Text('Please enter a name.'),
    actions: [
      TextButton(
        key: AppKeys.errorDialogOKButton, // 👈 and here
        onPressed: () => Navigator.of(context).pop(),
        child: Text('OK'),
      ),
    ],
  ),
);

🧪 Update test​

Now let's test the error scenario - what happens when users submit empty form? Let's clear the name field, submit it, and handle the error dialog that appears.

test/e2e_test.dart
// previous steps

await tt.type(AppKeys.nameField, '');
await tt.tap(AppKeys.submitButton);
await tt.exists(AppKeys.errorDialog);
await tt.tap(AppKeys.errorDialogOKButton);
await tt.absent(AppKeys.errorDialog);

💡 Pro Tips: The type action replaces existing text. The absent assertion is optional but excellent practice - it explicitly verifies the dialog actually disappeared, making your tests more reliable and self-documenting!

Run the test flutter test test and you should see the following output:

My E2E Widget test
...
✅ Typed "" into NameField
✅ Tapped SubmitButton
✅ ErrorDialog exists
✅ Tapped ErrorDialogOKButton
✅ ErrorDialog is absent
00:01 +1: All tests passed!

🎉 Achievement Unlocked!​

You've mastered error scenario testing! Your test now handles form validation, dialog interactions, and error recovery - all the messy edge cases that separate professional apps from amateur ones. And notice that even as our E2E test gets more and more advanced, it still completes under 1 second! 🚀

📚 Next steps​