Added unit tests for the event abstractions.
Added Element as the notion of common ancestry between Device and Host.
diff --git a/net/api/src/test/java/org/onlab/onos/event/TestListener.java b/net/api/src/test/java/org/onlab/onos/event/TestListener.java
new file mode 100644
index 0000000..ec2185a
--- /dev/null
+++ b/net/api/src/test/java/org/onlab/onos/event/TestListener.java
@@ -0,0 +1,19 @@
+package org.onlab.onos.event;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Test event listener fixture.
+ */
+public class TestListener implements EventListener<TestEvent> {
+
+ public final List<TestEvent> events = new ArrayList<>();
+
+ @Override
+ public void event(TestEvent event) {
+ events.add(event);
+ }
+
+}
+