[ONOS-4910, ONOS-4921] Framework: utils validation and defect fix

Change-Id: I821920fa8c88e64406b702c2b8736bdeaf231474
diff --git a/plugin/src/test/resources/default/DefaultCaseInChoiceSubStatement.yang b/plugin/src/test/resources/default/DefaultCaseInChoiceSubStatement.yang
new file mode 100644
index 0000000..72b597b
--- /dev/null
+++ b/plugin/src/test/resources/default/DefaultCaseInChoiceSubStatement.yang
@@ -0,0 +1,23 @@
+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    container food {
+       choice snack {
+           case sports-arena {
+               leaf pretzel {
+                   type string;
+               }
+               leaf beer {
+                   type string;
+               }
+           }
+           case late-night {
+               leaf chocolate {
+                   type string;
+               }
+           }
+           default "sports-arena";
+       }
+    }
+}