Flutter: How to test a method inside a Widgets State class? - unit-testing

Question

I have a widget test going for a Drawer which I named DefaultDrawer. I would also like to test the methods I made inside DefaultDrawerState. For example,
class DefaultDrawerState extends State<DefaultDrawer> {
#override
Widget build(BuildContext context) {
// ..build..
}
Widget _circleAvatar() {
// a method I want to test
}
}
How can I test the method _circleAvatar() when the flutter_test finders can't seem to call the methods within my widget or its state?
Below is my test file right now, without the testing of methods inside the widget:
void main() {
testWidgets('Drawer Test', (WidgetTester tester) async {
final key = GlobalKey<ScaffoldState>();
await tester.pumpWidget(
MaterialApp(home: Scaffold(key: key, drawer: DefaultDrawer())));
// open drawer
key.currentState.openDrawer();
await tester.pump();
// did drawer open?
final drawerFinder = find.byType(Drawer);
expect(drawerFinder, findsOneWidget);
});
}

Answer 1

To be able to test a Widget, you'd need to render the UI on the integration test using WidgetTester.pumpWidget(Widget). Let `SampleWidget
class SampleWidget {
Widget getWidget() {
return Container(
key: Key('SampleWidget'),
color: Colors.green,
);
}
}
... and on the test, call the Widget directly with widgetTester.pumpWidget(SampleWidget().getWidget()); to render it for the test.
void main() {
IntegrationTestWidgetsFlutterBinding.ensureInitialized();
testWidgets("Test Widget", (WidgetTester widgetTester) async {
bool found = false;
await widgetTester.pumpWidget(SampleWidget().getWidget());
widgetTester.allWidgets.forEach((Widget element) {
if(element.key.toString().contains('SampleWidget')){
debugPrint('Found Sample Widget!');
found = true;
}
});
expect(found, true);
});
}
The test should be able to find the widget element containing the key specified.
However, some Widgets on WidgetTester requires MaterialApp to be its parent. An example of this widget is Text - which requires Directionality, and Directionality can be found by using either MaterialApp or WidgetsApp widget. Rendering the Text Widget without MaterialApp on the test will fail. This error will be thrown.
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞════════════════════════
The following assertion was thrown building Text("Demo Widget"):
No Directionality widget found.
RichText widgets require a Directionality widget ancestor.
The specific widget that could not find a Directionality ancestor
was:
RichText
The ownership chain for the affected widget is: "RichText ← Text
← Center ← ColoredBox ← Container-[<'SampleWidget'>] ←
RepaintBoundary ← [root]"
Typically, the Directionality widget is introduced by the
MaterialApp or WidgetsApp widget at the top of your application
widget tree. It determines the ambient reading direction and is
used, for example, to determine how to lay out text, how to
interpret "start" and "end" values, and to resolve
EdgeInsetsDirectional, AlignmentDirectional, and other
*Directional objects.
As a workaround for this use case, you can wrap your Widget with MaterialApp.
class SampleWidget{
Widget getWidget() {
return MaterialApp(
home: Container(
key: Key('SampleWidget'),
color: Colors.green,
child: Center(
child: Text('Demo Widget'),
),
),
);
}
}