[ONOS-4762][ONOS-4601]Grammar for meta data +  Union defect fix

Change-Id: I8f78127e5b292cca6a79b32d496c2602c9105acd
diff --git a/utils/yangutils/plugin/src/test/java/org/onosproject/yangutils/parser/impl/listeners/UnionListenerTest.java b/utils/yangutils/plugin/src/test/java/org/onosproject/yangutils/parser/impl/listeners/UnionListenerTest.java
index 04b3796..1fe7218 100644
--- a/utils/yangutils/plugin/src/test/java/org/onosproject/yangutils/parser/impl/listeners/UnionListenerTest.java
+++ b/utils/yangutils/plugin/src/test/java/org/onosproject/yangutils/parser/impl/listeners/UnionListenerTest.java
@@ -138,4 +138,12 @@
 
         YangNode node = manager.getDataModel("src/test/resources/UnionWithEmptyType.yang");
     }
+
+    /**
+     * Checks whether type union has atleast one type statement.
+     */
+    @Test (expected = ParserException.class)
+    public void processUnionWithoutChild() throws IOException, ParserException {
+        manager.getDataModel("src/test/resources/UnionWithoutChild.yang");
+    }
 }