Does flutter_test support testing 'leaf' widgets? - flutter

Question

Suppose I create a simple widget, such as this:
class RightArrowButton extends StatelessWidget {
const RightArrowButton({VoidCallback onPressed})
: this._onPressed = onPressed;
final VoidCallback _onPressed;
#override
Widget build(BuildContext context) {
return IconButton(
visualDensity: VisualDensity.compact,
onPressed: _onPressed,
icon: _buildIcon(iconData()),
);
}
/// Overrride to set a different icon.
IconData iconData() => Icons.play_arrow;
Widget _buildIcon(IconData icon) => Icon(icon, color: Colors.blue);
}
Further suppose that I wish to unit test this widget. I know, this is an incredibly simple widget, but I might be attempting to use TDD to write the widget in the first place. In any case, I could apply the concept to a more complex widget.
In this case, the test would be very simple: Construct the widget, passing it an onPressed function whose side-effects can be checked to validate that the onPressed method is actually called when someone taps on the widget.
Sample test code:
void main() {
testWidgets('RightArrowButton', (WidgetTester tester) async {
int counter = 0;
await tester.pumpWidget(RightArrowButton(
onPressed: () => counter++,
));
expect(0, equals(counter));
var button = find.byType(IconButton);
await tester.tap(button);
expect(1, equals(counter));
});
}
However, when I do this, I get the following error:
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following assertion was thrown building IconButton(Icon, padding: EdgeInsets.all(8.0), dirty):
No Material widget found.
IconButton widgets require a Material widget ancestor.
I understand the error after reading this SO question:
No Material widget found
So -- Is there a way to unit test widgets in the way I want? Or am I forced to test a whole assembly of widgets in order to get a valid Material widget ancestor (which is more like a small integration test)?

Answer 1

I found a solution which works. Flutter experts, is the following approach the only or best way to achieve my goal of testing individual widgets in isolation?
void main() {
testWidgets('arrow test', (WidgetTester tester) async {
int counter = 0;
// must include Card to get Material;
// must include MaterialApp to get Directionality
await tester.pumpWidget(MaterialApp(
home: Card(
child: RightArrowButton(
onPressed: () => counter++,
),
),
));
await tester.tap(find.byType(RightArrowButton));
expect(1, equals(counter));
});
}