my overlay

my_overlay.dart

// error 
══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following assertion was thrown running a test:
Navigator operation requested with a context that does not include a Navigator.
The context used to push or pop routes from the Navigator must be that of a widget that is a
descendant of a Navigator widget.

// method

import 'package:dialog/overlayimage/overlay.dart';
import 'package:flutter/material.dart';

void showOverlayMethod(BuildContext context) {
  Navigator.of(context).push(
    MyOverlayImage(
      foregroundColor: Colors.red.withOpacity(.5),
    ),
  );
}

// test

import 'package:dialog/overlayimage/overlay.dart';
import 'package:dialog/show_overlay_method.dart';
import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:mocktail/mocktail.dart';
import 'package:network_image_mock/network_image_mock.dart';

class MockBuildContext extends Mock implements BuildContext {}

class MockNavigatorObserver extends Mock implements NavigatorObserver {}

void main() {
  TestWidgetsFlutterBinding.ensureInitialized();

  late BuildContext mockContext;
  late MockNavigatorObserver mockObserver;

  setUp(() {
    mockContext = MockBuildContext();
    mockObserver = MockNavigatorObserver();
  });

  setUpAll(() {
    registerFallbackValue(
      MyOverlayImage(
        foregroundColor: Colors.red.withOpacity(.5),
      ),
    );
  });

  testWidgets('showOverlayMethod navigates to MyOverlayImage', (tester) async {
    final myOverlay = MyOverlayImage(
      foregroundColor: Colors.red.withOpacity(.5),
    );

    await mockNetworkImagesFor(
      () => _createWidget(
        tester: tester,
        observer: mockObserver,
        route: myOverlay,
        context: mockContext,
        child: TextButton(
          onPressed: () => showOverlayMethod(mockContext),
          child: const Text('Show Overlay'),
        ),
      ),
    );

    showOverlayMethod(mockContext);

    final buttonFinder = find.byType(TextButton);

    expect(buttonFinder, findsOneWidget);

    await tester.tap(buttonFinder);

    await tester.pumpAndSettle();

    verify(() => mockObserver.didPush(any(), any())).called(1);

    expect(find.byType(MyOverlayImage), findsOneWidget);
  });
}

Future<void> _createWidget({
  required WidgetTester tester,
  required ModalRoute<void>? route,
  required NavigatorObserver observer,
  required BuildContext context,
  required Widget child,
}) async {
  await tester.pumpWidget(
    MaterialApp(
      navigatorObservers: [observer],
      onGenerateRoute: (settings) {
        return route;
      },
      home: Builder(
        builder: (context) => child,
      ),
    ),
  );
}