update test

+import 'package:flutter_test/flutter_test.dart';
+import 'package:get/utils.dart';
+
+void main() {
+  group('Test group for extension: isNullOrBlank', () {
+    String testString;
+    test('String extension: isNullOrBlank', () {
+      expect(testString.isNullOrBlank, equals(true));
+    });
+    test('String extension: isNullOrBlank', () {
+      testString = 'Not null anymore';
+      expect(testString.isNullOrBlank, equals(false));
+    });
+    test('String extension: isNullOrBlank', () {
+      testString = '';
+      expect(testString.isNullOrBlank, equals(true));
+    });
+  });
+}