string issue fix for few yang construct like config, mandatory + allowing yang constructs as identifers and string

Change-Id: I8dd01dc60d280a843b0a485681caa6bfcac013c2
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ConfigListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ConfigListenerTest.java
index fe20cad..7e693d5 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ConfigListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ConfigListenerTest.java
@@ -115,7 +115,7 @@
     @Test
     public void processConfigInvalidValue() throws IOException, ParserException {
         thrown.expect(ParserException.class);
-        thrown.expectMessage("mismatched input 'invalid' expecting {'false', 'true'}");
+        thrown.expectMessage("YANG file error : config value invalid is not valid.");
         YangNode node = manager.getDataModel("src/test/resources/ConfigInvalidValue.yang");
     }
 
@@ -125,7 +125,7 @@
     @Test
     public void processConfigEmptyValue() throws IOException, ParserException {
         thrown.expect(ParserException.class);
-        thrown.expectMessage("missing {'false', 'true'} at ';'");
+        thrown.expectMessage("no viable alternative at input ';'");
         YangNode node = manager.getDataModel("src/test/resources/ConfigEmptyValue.yang");
     }
 
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/MandatoryListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/MandatoryListenerTest.java
index 05ee69a..bc27dad 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/MandatoryListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/MandatoryListenerTest.java
@@ -126,7 +126,7 @@
     @Test
     public void processMandatoryEmptyStatement() throws IOException, ParserException {
         thrown.expect(ParserException.class);
-        thrown.expectMessage("missing {'false', 'true'} at ';'");
+        thrown.expectMessage("no viable alternative at input ';'");
         YangNode node = manager.getDataModel("src/test/resources/MandatoryEmptyStatement.yang");
     }
 
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/MinElementsListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/MinElementsListenerTest.java
index b197557..7f4a6f6 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/MinElementsListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/MinElementsListenerTest.java
@@ -111,7 +111,7 @@
     @Test
     public void processMinElementsInvalidValue() throws IOException, ParserException {
         thrown.expect(ParserException.class);
-        thrown.expectMessage("mismatched input 'asd' expecting INTEGER");
+        thrown.expectMessage("YANG file error : min-elements value asd is not valid.");
         YangNode node = manager.getDataModel("src/test/resources/MinElementsInvalidValue.yang");
     }
 
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/StatusListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/StatusListenerTest.java
index 6850425..984b0f2 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/StatusListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/StatusListenerTest.java
@@ -141,7 +141,7 @@
     @Test
     public void processStatusInvalidValue() throws IOException, ParserException {
         thrown.expect(ParserException.class);
-        thrown.expectMessage("mismatched input 'invalid' expecting {'current', 'deprecated', 'obsolete'}");
+        thrown.expectMessage("Invalid content in status \"invalid\" before processing.");
         YangNode node = manager.getDataModel("src/test/resources/StatusInvalidValue.yang");
     }