Improve tests logic

Author: solid-daniyilyevtyushkin

test/flutter_switch_test.dart

@@ -4,6 +4,9 @@ import 'package:flutter_test/flutter_test.dart';
 import '../lib/flutter_switch.dart';
 
 void main() {
+  final alignToggleIndicatorFinder = find.byWidgetPredicate(
+      (widget) => widget is Align && widget.child is Container);
+
   testWidgets(
     "displays the toggle indicator on the right if the given value is true",
     (WidgetTester tester) async {
@@ -13,7 +16,7 @@ void main() {
         ),
       );
 
-      final align = tester.widget<Align>(find.byType(Align));
+      final align = tester.widget<Align>(alignToggleIndicatorFinder);
 
       expect(align.alignment, equals(Alignment.centerRight));
     },
@@ -28,7 +31,7 @@ void main() {
         ),
       );
 
-      final align = tester.widget<Align>(find.byType(Align));
+      final align = tester.widget<Align>(alignToggleIndicatorFinder);
 
       expect(align.alignment, equals(Alignment.centerLeft));
     },