Add Unit tests for ClusterEvent

- override ClusterEvent's hashCode, equals, and toString

Change-Id: I85e3ff7d60b2c76559d71a4093cff73eee064cf9
diff --git a/core/api/src/test/java/org/onosproject/cluster/ClusterEventTest.java b/core/api/src/test/java/org/onosproject/cluster/ClusterEventTest.java
new file mode 100644
index 0000000..1351769
--- /dev/null
+++ b/core/api/src/test/java/org/onosproject/cluster/ClusterEventTest.java
@@ -0,0 +1,82 @@
+/*
+ * Copyright 2017-present 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.cluster;
+
+import com.google.common.testing.EqualsTester;
+import org.junit.Test;
+import org.onlab.packet.IpAddress;
+
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Unit tests for the cluster event test.
+ */
+public class ClusterEventTest {
+    private final NodeId node1 = new NodeId("1");
+    private final NodeId node2 = new NodeId("2");
+    private final IpAddress ip1 = IpAddress.valueOf("10.0.0.1");
+    private final IpAddress ip2 = IpAddress.valueOf("10.0.0.2");
+    private final ControllerNode cNode1 = new DefaultControllerNode(node1, ip1);
+    private final ControllerNode cNode2 = new DefaultControllerNode(node2, ip2);
+    private final ClusterEvent event1 =
+            new ClusterEvent(ClusterEvent.Type.INSTANCE_ADDED, cNode1);
+    private final ClusterEvent event2 =
+            new ClusterEvent(ClusterEvent.Type.INSTANCE_REMOVED, cNode1);
+    private final ClusterEvent event3 =
+            new ClusterEvent(ClusterEvent.Type.INSTANCE_ACTIVATED, cNode1);
+    private final ClusterEvent event4 =
+            new ClusterEvent(ClusterEvent.Type.INSTANCE_READY, cNode1);
+    private final ClusterEvent event5 =
+            new ClusterEvent(ClusterEvent.Type.INSTANCE_DEACTIVATED, cNode1);
+    private final ClusterEvent event6 =
+            new ClusterEvent(ClusterEvent.Type.INSTANCE_ADDED, cNode2);
+    private final long time = System.currentTimeMillis();
+    private final ClusterEvent event7 =
+            new ClusterEvent(ClusterEvent.Type.INSTANCE_READY, cNode2, time);
+    private final ClusterEvent sameAsEvent7 =
+            new ClusterEvent(ClusterEvent.Type.INSTANCE_READY, cNode2, time);
+
+    /**
+     * Tests for proper operation of equals(), hashCode() and toString() methods.
+     */
+    @Test
+    public void checkEquals() {
+        new EqualsTester()
+                .addEqualityGroup(event1)
+                .addEqualityGroup(event2)
+                .addEqualityGroup(event3)
+                .addEqualityGroup(event4)
+                .addEqualityGroup(event5)
+                .addEqualityGroup(event6)
+                .addEqualityGroup(event7, sameAsEvent7)
+                .testEquals();
+    }
+
+    /**
+     * Tests that objects are created properly.
+     */
+    @Test
+    public void checkConstruction() {
+        assertThat(event1.type(), is(ClusterEvent.Type.INSTANCE_ADDED));
+        assertThat(event1.subject(), is(cNode1));
+
+        assertThat(event7.time(), is(time));
+        assertThat(event7.type(), is(ClusterEvent.Type.INSTANCE_READY));
+        assertThat(event7.subject(), is(cNode2));
+    }
+
+}