diff --git a/cli/src/main/java/org/onlab/onos/cli/net/FlowsListCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/FlowsListCommand.java
index 12f6ee6..a9de51e 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/FlowsListCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/FlowsListCommand.java
@@ -33,6 +33,7 @@
             required = false, multiValued = false)
     String uri = null;
 
+
     @Override
     protected void execute() {
         DeviceService deviceService = get(DeviceService.class);
diff --git a/providers/openflow/link/src/main/java/org/onlab/onos/provider/of/link/impl/LinkDiscovery.java b/providers/openflow/link/src/main/java/org/onlab/onos/provider/of/link/impl/LinkDiscovery.java
index 1c98ad9..132b185 100644
--- a/providers/openflow/link/src/main/java/org/onlab/onos/provider/of/link/impl/LinkDiscovery.java
+++ b/providers/openflow/link/src/main/java/org/onlab/onos/provider/of/link/impl/LinkDiscovery.java
@@ -86,7 +86,7 @@
     private final boolean useBDDP;
     private final OpenFlowController ctrl;
     private final LinkProviderService linkProvider;
-    private final Map<Integer, OFPortDesc> ports;
+    protected final Map<Integer, OFPortDesc> ports;
     private Timeout timeout;
 
     /**
diff --git a/providers/openflow/link/src/main/java/org/onlab/onos/provider/of/link/impl/OpenFlowLinkProvider.java b/providers/openflow/link/src/main/java/org/onlab/onos/provider/of/link/impl/OpenFlowLinkProvider.java
index f448a44..f1e3861 100644
--- a/providers/openflow/link/src/main/java/org/onlab/onos/provider/of/link/impl/OpenFlowLinkProvider.java
+++ b/providers/openflow/link/src/main/java/org/onlab/onos/provider/of/link/impl/OpenFlowLinkProvider.java
@@ -29,6 +29,7 @@
 import org.projectfloodlight.openflow.protocol.OFPortStatus;
 import org.slf4j.Logger;
 
+
 /**
  * Provider which uses an OpenFlow controller to detect network
  * infrastructure links.
@@ -50,7 +51,7 @@
 
     private final InternalLinkProvider listener = new InternalLinkProvider();
 
-    private final Map<Dpid, LinkDiscovery> discoverers = new ConcurrentHashMap<>();
+    protected final Map<Dpid, LinkDiscovery> discoverers = new ConcurrentHashMap<>();
 
     /**
      * Creates an OpenFlow link provider.
@@ -138,7 +139,7 @@
 
         @Override
         public void roleAssertFailed(Dpid dpid, RoleState role) {
-            // TODO Auto-generated method stub
+            // do nothing for this.
         }
 
     }
diff --git a/providers/openflow/link/src/test/java/org/onlab/onos/provider/of/link/impl/OpenFlowLinkProviderTest.java b/providers/openflow/link/src/test/java/org/onlab/onos/provider/of/link/impl/OpenFlowLinkProviderTest.java
new file mode 100644
index 0000000..7fca158
--- /dev/null
+++ b/providers/openflow/link/src/test/java/org/onlab/onos/provider/of/link/impl/OpenFlowLinkProviderTest.java
@@ -0,0 +1,471 @@
+package org.onlab.onos.provider.of.link.impl;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.onlab.onos.net.ConnectPoint;
+import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.net.link.LinkDescription;
+import org.onlab.onos.net.link.LinkProvider;
+import org.onlab.onos.net.link.LinkProviderRegistry;
+import org.onlab.onos.net.link.LinkProviderService;
+import org.onlab.onos.net.provider.AbstractProviderService;
+import org.onlab.onos.net.provider.ProviderId;
+import org.onlab.onos.openflow.controller.Dpid;
+import org.onlab.onos.openflow.controller.OpenFlowPacketContext;
+import org.onlab.onos.openflow.controller.OpenFlowSwitch;
+import org.onlab.onos.openflow.controller.OpenFlowSwitchListener;
+import org.onlab.onos.openflow.controller.OpenflowControllerAdapter;
+import org.onlab.onos.openflow.controller.PacketListener;
+import org.onlab.onos.openflow.controller.RoleState;
+import org.onlab.packet.Ethernet;
+import org.onlab.packet.ONLabLddp;
+import org.projectfloodlight.openflow.protocol.OFFactory;
+import org.projectfloodlight.openflow.protocol.OFMessage;
+import org.projectfloodlight.openflow.protocol.OFPortConfig;
+import org.projectfloodlight.openflow.protocol.OFPortDesc;
+import org.projectfloodlight.openflow.protocol.OFPortReason;
+import org.projectfloodlight.openflow.protocol.OFPortStatus;
+import org.projectfloodlight.openflow.protocol.ver10.OFFactoryVer10;
+import org.projectfloodlight.openflow.types.OFPort;
+
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+
+public class OpenFlowLinkProviderTest {
+
+
+    private static final DeviceId DID1 = DeviceId.deviceId("of:0000000000000001");
+    private static final DeviceId DID2 = DeviceId.deviceId("of:0000000000000002");
+
+    private static final Dpid DPID2 = Dpid.dpid(DID2.uri());
+    private static final Dpid DPID1 = Dpid.dpid(DID1.uri());
+
+    private static final OFPortDesc PD1 = portDesc(1, true);
+    private static final OFPortDesc PD2 = portDesc(2, true);
+    private static final OFPortDesc PD3 = portDesc(1, true);
+    private static final OFPortDesc PD4 = portDesc(2, true);
+
+    private static final List<OFPortDesc> PLIST1 = Lists.newArrayList(PD1, PD2);
+    private static final List<OFPortDesc> PLIST2 = Lists.newArrayList(PD3, PD4);
+
+    private static final TestOpenFlowSwitch SW1 = new TestOpenFlowSwitch(DPID1, PLIST1);
+    private static final TestOpenFlowSwitch SW2 = new TestOpenFlowSwitch(DPID2, PLIST2);
+
+    private final OpenFlowLinkProvider provider = new OpenFlowLinkProvider();
+    private final TestLinkRegistry linkService = new TestLinkRegistry();
+    private final TestController controller = new TestController();
+
+    private TestLinkProviderService providerService;
+    private TestPacketContext pktCtx;
+
+    @Before
+    public void setUp() {
+        pktCtx = new TestPacketContext(DPID2);
+        provider.providerRegistry = linkService;
+        controller.switchMap.put(DPID1, SW1);
+        controller.switchMap.put(DPID2, SW2);
+        provider.controller = controller;
+        provider.activate();
+    }
+
+    @Test
+    public void basics() {
+        assertNotNull("registration expected", providerService);
+        assertEquals("incorrect provider", provider, providerService.provider());
+    }
+
+    @Test
+    public void switchAdd() {
+        controller.listener.switchAdded(DPID1);
+        assertFalse("Device not added", provider.discoverers.isEmpty());
+    }
+
+    @Test
+    public void switchRemove() {
+        controller.listener.switchAdded(DPID1);
+        controller.listener.switchRemoved(DPID1);
+
+        assertTrue("Discoverer is not gone", provider.discoverers.isEmpty());
+        assertTrue("Device is not gone.", vanishedDpid(DPID1));
+    }
+
+    @Test
+    public void portUp() {
+        controller.listener.switchAdded(DPID1);
+        controller.listener.portChanged(DPID1, portStatus(true, 3));
+
+        assertTrue("Port not added to discoverer",
+                provider.discoverers.get(DPID1).ports.containsKey(3));
+    }
+
+    @Test
+    public void portDown() {
+        controller.listener.switchAdded(DPID1);
+        controller.listener.portChanged(DPID1, portStatus(false, 1));
+
+        assertFalse("Port added to discoverer",
+                provider.discoverers.get(DPID1).ports.containsKey(1));
+        assertTrue("Port is not gone.", vanishedPort((long) 1));
+    }
+
+    @Test
+    public void portUnknown() {
+        controller.listener.switchAdded(DPID1);
+        controller.listener.portChanged(DPID2, portStatus(false, 1));
+
+        assertNull("DPID exists",
+                provider.discoverers.get(DPID2));
+    }
+
+    @Test
+    public void unknownPktCtx() {
+        controller.pktListener.handlePacket(pktCtx);
+
+        assertFalse("Context should still be free", pktCtx.isHandled());
+    }
+
+    @Test
+    public void knownPktCtx() {
+        controller.listener.switchAdded(DPID1);
+        controller.listener.switchAdded(DPID2);
+
+        controller.pktListener.handlePacket(pktCtx);
+
+        assertTrue("Link not detected", detectedLink(DPID1, DPID2));
+
+    }
+
+
+    @After
+    public void tearDown() {
+        provider.deactivate();
+        provider.providerRegistry = null;
+        provider.controller = null;
+    }
+
+    private OFPortStatus portStatus(boolean up, int port) {
+        OFPortDesc desc = portDesc(port, up);
+        OFPortStatus status = OFFactoryVer10.INSTANCE.buildPortStatus()
+                .setDesc(desc)
+                .setReason(up ? OFPortReason.ADD : OFPortReason.DELETE).build();
+        return status;
+
+    }
+
+    private static OFPortDesc portDesc(int port, boolean up) {
+        OFPortDesc.Builder builder = OFFactoryVer10.INSTANCE.buildPortDesc();
+        builder.setPortNo(OFPort.of(port));
+        if (!up) {
+            builder.setConfig(Collections.singleton(OFPortConfig.PORT_DOWN));
+        }
+        return builder.build();
+    }
+
+    private boolean vanishedDpid(Dpid... dpids) {
+        for (int i = 0; i < dpids.length; i++) {
+            if (!providerService.vanishedDpid.contains(dpids[i])) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private boolean vanishedPort(Long... ports) {
+        for (int i = 0; i < ports.length; i++) {
+            if (!providerService.vanishedPort.contains(ports[i])) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private boolean detectedLink(Dpid src, Dpid dst) {
+        for (Dpid key : providerService.discoveredLinks.keySet()) {
+            if (key.equals(src)) {
+                return providerService.discoveredLinks.get(src).equals(dst);
+            }
+        }
+        return false;
+    }
+
+
+    private class TestLinkRegistry implements LinkProviderRegistry {
+
+        @Override
+        public LinkProviderService register(LinkProvider provider) {
+            providerService = new TestLinkProviderService(provider);
+            return providerService;
+        }
+
+        @Override
+        public void unregister(LinkProvider provider) {
+        }
+
+        @Override
+        public Set<ProviderId> getProviders() {
+            return null;
+        }
+
+    }
+
+    private class TestLinkProviderService
+    extends AbstractProviderService<LinkProvider>
+    implements LinkProviderService {
+
+        List<Dpid> vanishedDpid = Lists.newLinkedList();
+        List<Long> vanishedPort = Lists.newLinkedList();
+        Map<Dpid, Dpid> discoveredLinks = Maps.newHashMap();
+
+        protected TestLinkProviderService(LinkProvider provider) {
+            super(provider);
+        }
+
+        @Override
+        public void linkDetected(LinkDescription linkDescription) {
+            Dpid sDpid = Dpid.dpid(linkDescription.src().deviceId().uri());
+            Dpid dDpid = Dpid.dpid(linkDescription.dst().deviceId().uri());
+            discoveredLinks.put(sDpid, dDpid);
+        }
+
+        @Override
+        public void linkVanished(LinkDescription linkDescription) {
+            // TODO Auto-generated method stub
+
+        }
+
+        @Override
+        public void linksVanished(ConnectPoint connectPoint) {
+            vanishedPort.add(connectPoint.port().toLong());
+
+        }
+
+        @Override
+        public void linksVanished(DeviceId deviceId) {
+            vanishedDpid.add(Dpid.dpid(deviceId.uri()));
+        }
+
+
+    }
+
+    private class TestController extends OpenflowControllerAdapter {
+        PacketListener pktListener;
+        OpenFlowSwitchListener listener;
+        Map<Dpid, OpenFlowSwitch> switchMap = new HashMap<Dpid, OpenFlowSwitch>();
+
+        @Override
+        public void addPacketListener(int priority, PacketListener listener) {
+            pktListener = listener;
+        }
+
+        @Override
+        public void removePacketListener(PacketListener listener) {
+            pktListener = null;
+        }
+
+        @Override
+        public void addListener(OpenFlowSwitchListener listener) {
+            this.listener = listener;
+        }
+
+        @Override
+        public void removeListener(OpenFlowSwitchListener listener) {
+            this.listener = null;
+        }
+
+        @Override
+        public void processPacket(Dpid dpid, OFMessage msg) {
+            OpenFlowPacketContext ctx = new TestPacketContext(dpid);
+            pktListener.handlePacket(ctx);
+        }
+
+        @Override
+        public Iterable<OpenFlowSwitch> getSwitches() {
+            return Collections.emptyList();
+        }
+
+        @Override
+        public OpenFlowSwitch getSwitch(Dpid dpid) {
+            return switchMap.get(dpid);
+        }
+    }
+
+
+
+    private class TestPacketContext implements OpenFlowPacketContext {
+
+        protected Dpid swid;
+        protected boolean blocked = false;
+
+        public TestPacketContext(Dpid dpid) {
+            swid = dpid;
+        }
+
+        @Override
+        public boolean block() {
+            blocked = true;
+            return blocked;
+        }
+
+        @Override
+        public void send() {
+        }
+
+        @Override
+        public void build(OFPort outPort) {
+        }
+
+        @Override
+        public void build(Ethernet ethFrame, OFPort outPort) {
+        }
+
+        @Override
+        public Ethernet parsed() {
+            return null;
+        }
+
+        @Override
+        public byte[] unparsed() {
+            ONLabLddp lldp = new ONLabLddp();
+            lldp.setSwitch(DPID1.value());
+
+            Ethernet ethPacket = new Ethernet();
+            ethPacket.setEtherType(Ethernet.TYPE_LLDP);
+            ethPacket.setDestinationMACAddress(ONLabLddp.LLDP_NICIRA);
+            ethPacket.setPayload(lldp);
+            ethPacket.setPad(true);
+
+
+            lldp.setPort(PD1.getPortNo().getPortNumber());
+            ethPacket.setSourceMACAddress(PD1.getHwAddr().getBytes());
+            return ethPacket.serialize();
+
+        }
+
+        @Override
+        public Dpid dpid() {
+            return swid;
+        }
+
+        @Override
+        public Integer inPort() {
+            return PD3.getPortNo().getPortNumber();
+        }
+
+        @Override
+        public boolean isHandled() {
+            return blocked;
+        }
+
+        @Override
+        public boolean isBuffered() {
+            return false;
+        }
+
+    }
+
+    private static class TestOpenFlowSwitch implements OpenFlowSwitch {
+
+        private final List<OFPortDesc> ports;
+        private final Dpid dpid;
+
+        public TestOpenFlowSwitch(Dpid dpid, List<OFPortDesc> ports) {
+            this.ports = ports;
+            this.dpid = dpid;
+        }
+
+        RoleState state;
+        List<OFMessage> sent = new ArrayList<OFMessage>();
+        OFFactory factory = OFFactoryVer10.INSTANCE;
+
+        @Override
+        public void sendMsg(OFMessage msg) {
+            sent.add(msg);
+        }
+
+        @Override
+        public void sendMsg(List<OFMessage> msgs) {
+        }
+
+        @Override
+        public void handleMessage(OFMessage fromSwitch) {
+        }
+
+        @Override
+        public void setRole(RoleState role) {
+            state = role;
+        }
+
+        @Override
+        public RoleState getRole() {
+            return state;
+        }
+
+        @Override
+        public List<OFPortDesc> getPorts() {
+            return ports;
+        }
+
+        @Override
+        public OFFactory factory() {
+            return factory;
+        }
+
+        @Override
+        public String getStringId() {
+            return null;
+        }
+
+        @Override
+        public long getId() {
+            return dpid.value();
+        }
+
+        @Override
+        public String manfacturerDescription() {
+            return null;
+        }
+
+        @Override
+        public String datapathDescription() {
+            return null;
+        }
+
+        @Override
+        public String hardwareDescription() {
+            return null;
+        }
+
+        @Override
+        public String softwareDescription() {
+            return null;
+        }
+
+        @Override
+        public String serialNumber() {
+            return null;
+        }
+
+        @Override
+        public void disconnectSwitch() {
+        }
+
+        @Override
+        public void returnRoleAssertFailure(RoleState role) {
+        }
+
+    }
+}