Test should find a specific icon

How can I test that it should find a specific Icon like Icons.visibility? This is my test:

  testWidgets(
      'Should find visibility_off icon',
      (WidgetTester tester) async {
    await _buildApp(tester);
    await tester.pumpAndSettle();
    expect(find.byWidget(Icon(Icons.visibility)), findsOneWidget);
  });