add tests

lib/core/controller/controller.dart

@@ -144,7 +144,6 @@ class CanvasController with ChangeNotifier {
     if (!_init) return [];
 
     final idsToBuild = _childrenWithinBuildArea(_gsCenter, _buildExtent);
-    print("building ${idsToBuild.length} widgets at ${_gsCenter.toPoint()} with extent ${_buildExtent.toPoint()}");
 
     return idsToBuild.map((id) {
       final item = _children[id]!;

test/canvas_view_test.dart

@@ -0,0 +1,73 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter/material.dart';
+import 'package:infinite_lazy_2d_grid/core/render.dart';
+import 'package:infinite_lazy_2d_grid/core/controller/controller.dart';
+import 'package:infinite_lazy_2d_grid/core/background.dart';
+
+class TestChild extends StatelessWidget {
+  final int index;
+  const TestChild({required this.index, super.key});
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(child: SizedBox(key: ValueKey('test_child_$index'), width: 50, height: 50));
+  }
+}
+
+void main() {
+  testWidgets('CanvasView renders only visible children and reduces count on zoom out', (WidgetTester tester) async {
+    final controller = CanvasController(debug: true, initialScale: 1);
+    for (int i = 0; i < 10000; i++) {
+      controller.addChild(Offset((i % 80) * 100.0, (i ~/ 80) * 100.0), () => TestChild(index: i));
+    }
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: CanvasView(controller: controller, canvasBackground: SingleColorBackround(Colors.white)),
+        ),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    final initialChildren = find.byType(TestChild);
+    final initialCount = tester.widgetList(initialChildren).length;
+
+    // should be less than 10000 children rendered (only those part of the visible viewport)
+    expect(initialCount, lessThan(10000));
+    expect(initialCount, greaterThan(0));
+
+    controller.updateScalebyDelta(1); // 2x zoom in
+    await tester.pumpAndSettle();
+
+    // After zooming out, fewer children should be visible
+    final afterZoomChildren = find.byType(TestChild);
+    final afterZoomCount = tester.widgetList(afterZoomChildren).length;
+    expect(afterZoomCount, lessThan(initialCount));
+    expect(afterZoomCount, greaterThan(0));
+  });
+
+  testWidgets('CanvasView scales as expected', (WidgetTester tester) async {
+    final controller = CanvasController(debug: true, initialScale: 1);
+    controller.addChild(const Offset(0, 0), () => TestChild(index: 0));
+    controller.addChild(const Offset(100, 100), () => TestChild(index: 1));
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: CanvasView(controller: controller, canvasBackground: SingleColorBackround(Colors.white)),
+        ),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    // Initial size check
+    final finder = find.byType(TestChild);
+    expect(finder, findsNWidgets(2));
+
+    // Simulate a scale update to 2x, keeping the top-left at (0,0)
+    controller.onScaleStart(ScaleStartDetails(focalPoint: const Offset(0, 0)));
+    controller.onScaleUpdate(ScaleUpdateDetails(focalPoint: const Offset(0, 0), scale: 2.0));
+    await tester.pumpAndSettle();
+    expect(controller.scale, 2.0);
+    final ssPositions = controller.widgetsWithScreenPositions().map((e) => e.ssPosition).toList();
+    expect(ssPositions, [Offset.zero, const Offset(200, 200)]);
+  });
+}