Repository: flutter/flutter
File: packages/flutter/test/widgets/widgets_app_tester.dart (Dart)

Code before:
    this.navigatorKey,
    this.home,
    this.routes = const <String, WidgetBuilder>{},
    this.color = const Color(0xFFFFFFFF),
    this.transitionsBuilder = _defaultTransitionsBuilder,
  });

  /// A key to use when building the [Navigator].
  ///
  /// If provided, this key can be used to access the [NavigatorState]
  /// directly for navigation operations in tests.
  final GlobalKey<NavigatorState>? navigatorKey;

  /// The widget to display within the app.
  final Widget? home;

  /// The application's top-level routing table.
  ///
  /// When a named route is pushed with [Navigator.pushNamed], the route name is
  /// looked up in this map. If the name is present, the associated
  /// [WidgetBuilder] is used to construct a [PageRouteBuilder] with zero-duration
  /// transitions by default.
  ///
  /// Defaults to an empty map.
  final Map<String, WidgetBuilder> routes;

  /// The primary color for the application.
  ///
  /// Defaults to white.
  final Color color;

  /// The transition builder used for page route animations.
  ///
  /// Defaults to no transition (returns child directly) for simpler testing.
  /// Override this if you need to test specific transition animations.
  final RouteTransitionsBuilder transitionsBuilder;

  static Widget _defaultTransitionsBuilder(
    BuildContext context,
    Animation<double> animation,
    Animation<double> secondaryAnimation,
    Widget child,
  ) => child;

  @override
  Widget build(BuildContext context) {
    return WidgetsApp(
      color: color,
      navigatorKey: navigatorKey,
      home: home,
      routes: routes,

Review comment (suggestion):
I think for each property we should link it to the `WidgetsApp` equivalent. And here we have a brief summary + its use case in tests.

Code after:
    super.key,
    this.navigatorKey,
    this.home,
    this.routes = const <String, WidgetBuilder>{},
    this.color = const Color(0xFFFFFFFF),
    this.pageRouteBuilder = _defaultPageRouteBuilder,
  });

  /// A key to use when building the [Navigator].
  ///
  /// In tests, this allows direct access to the [NavigatorState] for
  /// programmatic navigation without needing to find the [Navigator] widget:
  ///
  /// ```dart
  /// final navigatorKey = GlobalKey<NavigatorState>();
  /// await tester.pumpWidget(TestWidgetsApp(
  ///   navigatorKey: navigatorKey,
  ///   home: const Text('Home'),
  /// ));
  /// navigatorKey.currentState!.pushNamed('/details');
  /// ```
  ///
  /// See also:
  ///
  ///  * [WidgetsApp.navigatorKey], the equivalent property in [WidgetsApp].
  final GlobalKey<NavigatorState>? navigatorKey;

  /// The widget displayed when the app launches.
  ///
  /// In tests, this is where you place the widget under test. The widget
  /// will have access to [Navigator], [Overlay], and other app-level
  /// services provided by [WidgetsApp].
  ///
  /// See also:
  ///
  ///  * [WidgetsApp.home], the equivalent property in [WidgetsApp].
  final Widget? home;

  /// The application's top-level routing table.
  ///
  /// Maps route names to widget builders. When navigating to a named route,
  /// the corresponding builder is called to create the route's content.
  ///
  /// In tests, routes are built using [pageRouteBuilder], which defaults to
  /// zero-duration transitions for instant navigation without waiting for
  /// animations.
  ///
  /// Defaults to an empty map.
  ///
  /// See also:
  ///