Added some tests.
diff --git a/net/api/src/main/java/org/onlab/onos/net/provider/ProviderRegistry.java b/net/api/src/main/java/org/onlab/onos/net/provider/ProviderRegistry.java
index 93436fc..08975e2 100644
--- a/net/api/src/main/java/org/onlab/onos/net/provider/ProviderRegistry.java
+++ b/net/api/src/main/java/org/onlab/onos/net/provider/ProviderRegistry.java
@@ -1,5 +1,7 @@
 package org.onlab.onos.net.provider;
 
+import java.util.Set;
+
 /**
  * Registry for tracking information providers with the core.
  *
@@ -29,4 +31,11 @@
      */
     void unregister(P provider);
 
+    /**
+     * Returns a set of currently registered provider identities.
+     *
+     * @return set of provider identifiers
+     */
+    Set<ProviderId> getProviders();
+
 }