improve extensions widget test

@@ -2,10 +2,17 @@ import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:get/utils.dart';
 
+class Foo extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return SizedBox.shrink();
+  }
+}
+
 void main() {
   group('Group test for PaddingX Extension', () {
     testWidgets('Test of paddingAll', (tester) async {
-      Widget containerTest = Container();
+      Widget containerTest = Foo();
 
       expect(find.byType(Padding), findsNothing);
 
@@ -15,7 +22,7 @@ void main() {
     });
 
     testWidgets('Test of paddingOnly', (tester) async {
-      Widget containerTest = Container();
+      Widget containerTest = Foo();
 
       expect(find.byType(Padding), findsNothing);
 
@@ -25,7 +32,7 @@ void main() {
     });
 
     testWidgets('Test of paddingSymmetric', (tester) async {
-      Widget containerTest = Container();
+      Widget containerTest = Foo();
 
       expect(find.byType(Padding), findsNothing);
 
@@ -35,7 +42,7 @@ void main() {
     });
 
     testWidgets('Test of paddingZero', (tester) async {
-      Widget containerTest = Container();
+      Widget containerTest = Foo();
 
       expect(find.byType(Padding), findsNothing);
 
@@ -47,7 +54,7 @@ void main() {
 
   group('Group test for MarginX Extension', () {
     testWidgets('Test of marginAll', (tester) async {
-      Widget containerTest = Container();
+      Widget containerTest = Foo();
 
       await tester.pumpWidget(containerTest.marginAll(16));
 
@@ -55,7 +62,7 @@ void main() {
     });
 
     testWidgets('Test of marginOnly', (tester) async {
-      Widget containerTest = Container();
+      Widget containerTest = Foo();
 
       await tester.pumpWidget(containerTest.marginOnly(top: 16));
 
@@ -63,7 +70,7 @@ void main() {
     });
 
     testWidgets('Test of marginSymmetric', (tester) async {
-      Widget containerTest = Container();
+      Widget containerTest = Foo();
 
       await tester.pumpWidget(containerTest.marginSymmetric(vertical: 16));
 
@@ -71,7 +78,7 @@ void main() {
     });
 
     testWidgets('Test of marginZero', (tester) async {
-      Widget containerTest = Container();
+      Widget containerTest = Foo();
 
       await tester.pumpWidget(containerTest.marginZero);