diff --git a/example/example.dart b/example/example.dart
index 24a92d2..1ad7ed4 100644
--- a/example/example.dart
+++ b/example/example.dart
@@ -1,5 +1,6 @@
 import 'package:configurable/dotenv_configuration_provider.dart';
 import 'package:configurable/simple_configuration_provider.dart';
+import 'package:configurable/system_config.dart';
 
 void main() {
   var key = 'app.name';
@@ -7,9 +8,16 @@ void main() {
 
   // in-memory provider (built-in)
   var simpleProvider = SimpleConfigurationProvider();
+  SystemConfig.setProvider(simpleProvider);
+  var result1 = SystemConfig.getOrNull(key, defaultValue: value);
+  // output: CUBETIQ Solution
+  print(result1);
 
   // dotenv provider (from file .env)
   var dotenvProvider = DotenvConfigurationProvider();
+  SystemConfig.setProvider(dotenvProvider);
+  var result2 = SystemConfig.getOrNull('HOME');
 
-  
+  // output: user's home directory
+  print(result2);
 }
\ No newline at end of file
diff --git a/test/config_test.dart b/test/config_test.dart
index e420b67..b79cff1 100644
--- a/test/config_test.dart
+++ b/test/config_test.dart
@@ -1,4 +1,4 @@
-import 'package:configurable/configurable.dart' show getConfigOrNull;
+import 'package:configurable/configurable.dart' show getConfigOrNull, hasConfigkey;
 import 'package:configurable/dotenv_configuration_provider.dart';
 import 'package:configurable/system_config.dart';
 import 'package:test/test.dart';
@@ -33,6 +33,7 @@ void main() {
     var result = getConfigOrNull(key, defaultValue: value);
 
     expect(value, equals(result));
+    expect(true, equals(hasConfigkey(key)));
     expect(value, equals(getConfigOrNull(key)));
   });
 }