Testing building Flutter widget throws Exception

Question

Is there a way to test for building a widget throwing an exception.

I tried this in testWidgets but it doesn't recognize the error.

expectLater(() async {
  await tester.pumpWidget(...);
}, throwsException);

You probably want to throw on the constructor instead of build. — Rémi Rousselet
– Rémi Rousselet, Commented Nov 12, 2018 at 7:13

Günter Zöchbauer · Accepted Answer · 2018-11-12 06:59:52Z

2

You can only catch exceptions thrown by code invoked by your code.
build() is invoked by the Flutter framework and therefore errors land there.

You can register a custom error handler for such exceptions in your test

final errorHandled = expectAsync0((){});

FlutterError.onError = (errorDetails) {
  // handle error
  errorHandled();
});

This way the test will fail if errorHandled isn't called before the test times out.

answered Nov 12, 2018 at 6:59

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