[ONOS-3247] Add the junit test code of SubnetId

Change-Id: Ifc205e24ff8ef28bf86afbf495abb7133e5fd788

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.vtnrsc.subnet;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.notNullValue;
+import static org.onlab.junit.ImmutableClassChecker.assertThatClassIsImmutable;
+
+import org.junit.Test;
+import org.onosproject.vtnrsc.SubnetId;
+
+import com.google.common.testing.EqualsTester;
+
+/**
+ * Unit tests for SubnetId class.
+ */
+public class SubnetIdTest {
+
+    final SubnetId subnetId1 = SubnetId.subnetId("1");
+    final SubnetId sameAsSubnetId1 = SubnetId.subnetId("1");
+    final SubnetId subnetId2 = SubnetId.subnetId("2");
+
+    /**
+     * Checks that the SubnetId class is immutable.
+     */
+    @Test
+    public void testImmutability() {
+        assertThatClassIsImmutable(SubnetId.class);
+    }
+
+    /**
+     * Checks the operation of equals() methods.
+     */
+    @Test
+    public void testEquals() {
+        new EqualsTester().addEqualityGroup(subnetId1, sameAsSubnetId1).addEqualityGroup(subnetId2)
+                .testEquals();
+    }
+
+    /**
+     * Checks the construction of a SubnetId object.
+     */
+    @Test
+    public void testConstruction() {
+        final String subnetIdValue = "s";
+        final SubnetId subnetId = SubnetId.subnetId(subnetIdValue);
+        assertThat(subnetId, is(notNullValue()));
+        assertThat(subnetId.subnetId(), is(subnetIdValue));
+    }
+}