How to test navigation via Navigator in Flutter
In the navigator tests in the flutter repo they use the NavigatorObserver class to observe navigations:
class TestObserver extends NavigatorObserver {
OnObservation onPushed;
OnObservation onPopped;
OnObservation onRemoved;
OnObservation onReplaced;
@override
void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
if (onPushed != null) {
onPushed(route, previousRoute);
}
}
@override
void didPop(Route<dynamic> route, Route<dynamic> previousRoute) {
if (onPopped != null) {
onPopped(route, previousRoute);
}
}
@override
void didRemove(Route<dynamic> route, Route<dynamic> previousRoute) {
if (onRemoved != null)
onRemoved(route, previousRoute);
}
@override
void didReplace({ Route<dynamic> oldRoute, Route<dynamic> newRoute }) {
if (onReplaced != null)
onReplaced(newRoute, oldRoute);
}
}
This looks like it should do what you want, however it may only work form the top level (MaterialApp), I'm not sure if you can provide it to just a widget.
This is modified version of the other answer to show how to do it with mocktail instead of mockito:
import 'package:mocktail/mocktail.dart';
class MockNavigatorObserver extends Mock implements NavigatorObserver {}
class FakeRoute extends Fake implements Route {}
void main() {
setUpAll(() {
registerFallbackValue(FakeRoute());
});
testWidgets('Button is present and triggers navigation after tapped',
(WidgetTester tester) async {
final mockObserver = MockNavigatorObserver();
await tester.pumpWidget(
MaterialApp(
home: MyScreen(),
navigatorObservers: [mockObserver],
),
);
expect(find.byType(RaisedButton), findsOneWidget);
await tester.tap(find.byType(RaisedButton));
await tester.pumpAndSettle();
verify(mockObserver.didPush(any(), any()));
expect(find.byType(DetailsPage), findsOneWidget);
});
}
While what Danny said is correct and works, you can also create a mocked NavigatorObserver to avoid any extra boilerplate:
import 'package:mockito/mockito.dart';
class MockNavigatorObserver extends Mock implements NavigatorObserver {}
That would translate to your test case as follows:
void main() {
testWidgets('Button is present and triggers navigation after tapped',
(WidgetTester tester) async {
final mockObserver = MockNavigatorObserver();
await tester.pumpWidget(
MaterialApp(
home: MyScreen(),
navigatorObservers: [mockObserver],
),
);
expect(find.byType(RaisedButton), findsOneWidget);
await tester.tap(find.byType(RaisedButton));
await tester.pumpAndSettle();
/// Verify that a push event happened
verify(mockObserver.didPush(any, any));
/// You'd also want to be sure that your page is now
/// present in the screen.
expect(find.byType(DetailsPage), findsOneWidget);
});
}
I wrote an in-depth article about this on my blog, which you can find here.