[ONOS-4753] Identity/identityref implementation and UT

Change-Id: I40148fa228465555be3bdf410cc294ffc0f34c18
diff --git a/plugin/src/test/resources/interfileidentityimportdependencyUndefined/featurefile1.yang b/plugin/src/test/resources/interfileidentityimportdependencyUndefined/featurefile1.yang
new file mode 100644
index 0000000..ec2e48c
--- /dev/null
+++ b/plugin/src/test/resources/interfileidentityimportdependencyUndefined/featurefile1.yang
@@ -0,0 +1,29 @@
+module syslog1 {
+     yang-version 1;
+     namespace "http://huawei1.com";
+     prefix "sys1";
+
+     import "syslog2" {
+        prefix "sys2";
+     }
+
+     identity ipv4-address-family {
+        base sys2:ref-address-family;
+     }
+
+     identity ipv6-address-family {
+        base sys2:ref-address-family;
+     }
+
+    leaf tunnel {
+        type identityref {
+            base sys2:ref-address-family;
+        }
+    }
+
+    leaf-list network-ref {
+        type identityref {
+            base sys2:ref-address-family;
+        }
+    }
+}
diff --git a/plugin/src/test/resources/interfileidentityimportdependencyUndefined/featurefile2.yang b/plugin/src/test/resources/interfileidentityimportdependencyUndefined/featurefile2.yang
new file mode 100644
index 0000000..25e66af
--- /dev/null
+++ b/plugin/src/test/resources/interfileidentityimportdependencyUndefined/featurefile2.yang
@@ -0,0 +1,18 @@
+module syslog2 {
+     yang-version 1;
+     namespace "http://huawei2.com";
+     prefix "sys2";
+
+     import "syslog3" {
+        prefix "sys3";
+     }
+
+     identity tunnel-type {
+         base sys3:final-address-family;
+     }
+
+     identity ref-address-family {
+         base sys3:final-address-family;
+     }
+}
+
diff --git a/plugin/src/test/resources/interfileidentityimportdependencyUndefined/featurefile3.yang b/plugin/src/test/resources/interfileidentityimportdependencyUndefined/featurefile3.yang
new file mode 100644
index 0000000..f638139
--- /dev/null
+++ b/plugin/src/test/resources/interfileidentityimportdependencyUndefined/featurefile3.yang
@@ -0,0 +1,5 @@
+module syslog3 {
+     yang-version 1;
+     namespace "http://huawei3.com";
+     prefix "sys3";
+}