Document the flutter_test dimensions and describe tricks for testing other dimensions

Currently the size is fixed at 800 x 600, which makes it impossible to test behavior that happens only in portrait mode, as well as other size-dependent behavior.

Potential options:

Support flags to flutter_tester that affect the screen resolution in test_runner.cc
~~Make AutomatedTestWidgetsFlutterBinding override createViewConfiguration() (like LiveTestWidgetsFlutterBinding does) to look for some hook to override the default resolution.~~

Actually it looks like:

#1 above is required.
That will make AutomatedTestWidgetsFlutterBinding automatically pick up the desired resolution.
We would need to update LiveTestWidgetsFlutterBinding to provide a hook whereby the developer could specify the fixed resolution in which they want to run. Otherwise, even though the real test was run in a resolution specified by the developer, a flutter run invocation of that test would yield a different resolution.

Just wrap the widget under test in a SizedBox (contained in a Center) with the given size. Optionally add a MediaQuery in there too if that matters.

Thanks, Hixie. That seems to work, but it's entirely non-obvious. It would be good to provide a better API.

We should definitely document it, maybe provide some arguments to pumpWidget to do it for you.

IIRC the current default size isn't documented anywhere. That might be helpful to document too.

Not sure how much this is related but it would be useful if we could take full-page screenshots of entire widgets for screenshot tests. For example: if you have a ListView that extends beyond the default viewport, the screenshot would capture the entire ListView. Also, if you have a widget less than the default viewport, it could capture an image that's just that widget's size.

At least the second use case is possible by inserting a RepaintBoundary in the hierarchy where you want to cap the screenshot.

ListViews don't go beyond the viewport. That's sort of the entire point of a ListView. :-) They don't even reify the widgets that aren't visible.

You could always create a RepaintBoundary around a SizedBox that is the size you want, though, and put the ListView inside that.

@johnfesa

Thanks, Todd. That's exactly what I was looking for.

Ian, I guess maybe what I'm asking for just not possible to implement with the design of ListViews. I'm basically asking for what you describe in your second paragraph but for it to somehow know how large the screen is. Maybe we could create our own implementation by scrolling the screen down until it won't scroll anymore and determining the height. cc @johnfesa

@Hixie

@Hixie, @paolosoares reports that he'd like to not just change the size of the produced image -- he'd like to change the constraints so that the widget lays out differently.

Is there any solution to this? I can't get my widget test to run because of a phantom overflow somewhere.

I tried adjusting MediaQuery and this:

        final size = Size(414, 896);
        await binding.setSurfaceSize(size);
        binding.window.physicalSizeTestValue = size;
        tester.binding.window.devicePixelRatioTestValue = 1;

But I can't fix this overflow. Those dimensions are the same as the iphone simulator and it runs fine in that. How can we fix widget test sizing?

Just wrap the widget under test in a SizedBox (contained in a Center) with the given size. Optionally add a MediaQuery in there too if that matters.

For simulating screen rotation, it seems that the SizedBox + MediaQuery approach might not behave quite like an actual screen rotation on a device. I've observed an actual screen rotation triggering Layer.attach without triggering Layer.addToScene, but changing the dimensions of a SizedBox seems to trigger both.

flutter/website#2005 is relevant as well here

This worked for me

setUp(() {
  WidgetsBinding.instance.renderView.configuration =  new TestViewConfiguration(size: const Size(1200.0, 1980.0));
});

it was just magic when dealing with an app made for a tablet. thank you!

The correct way to do this is to call setSurfaceSize on the binding.

E.g.

tester.binding.setSurfaceSize(size);

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

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Document the flutter_test dimensions and describe tricks for testing other dimensions #12994

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Document the flutter_test dimensions and describe tricks for testing other dimensions #12994

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tvolkert commented on Nov 13, 2017

tvolkert commented on Nov 13, 2017

Hixie commented on Nov 13, 2017

robertoscaramuzzi commented on Nov 14, 2017

Hixie commented on Nov 14, 2017

alanrussian commented on Dec 8, 2017

alanrussian commented on May 21, 2018

tvolkert commented on May 21, 2018

Hixie commented on May 21, 2018

alanrussian commented on May 21, 2018

tvolkert commented on Jun 12, 2018

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