Test empty string

Author: tvdijen

tests/Assert/NCNameTest.php

@@ -42,7 +42,10 @@ public static function provideNCName(): array
         return [
             [true, 'Test'],
             [true, '_Test'],
-            [true, '_5425e58e-e799-4884-92cc-ca64ecede32f'], // prefixed v4 UUID
+            // Prefixed v4 UUID
+            [true, '_5425e58e-e799-4884-92cc-ca64ecede32f'],
+            // An empty value is not valid, unless xsi:nil is used
+            [false, ''],
             [false, 'Te*st'],
             [false, '1Test'],
             [false, 'Te:st'],