diff --git a/src/main/java/net/floodlightcontroller/linkdiscovery/internal/LinkStorageImpl.java b/src/main/java/net/floodlightcontroller/linkdiscovery/internal/LinkStorageImpl.java
index ac76def..91a225d 100644
--- a/src/main/java/net/floodlightcontroller/linkdiscovery/internal/LinkStorageImpl.java
+++ b/src/main/java/net/floodlightcontroller/linkdiscovery/internal/LinkStorageImpl.java
@@ -200,7 +200,23 @@
 	// TODO: Fix me
 	@Override
 	public List<Link> getLinks(Long dpid, short port) {
-    	List<Link> links = null;
+    	List<Link> links = new ArrayList<Link>();
+    	
+    	IPortObject srcPort = dbop.searchPort(HexString.toHexString(dpid), port);
+    	ISwitchObject srcSw = srcPort.getSwitch();
+    	
+    	if(srcSw != null) {
+        	for(IPortObject dstPort : srcPort.getLinkedPorts()) {
+        		ISwitchObject dstSw = dstPort.getSwitch();
+        		Link link = new Link(HexString.toLong(srcSw.getDPID()),
+        				srcPort.getNumber(),
+        				HexString.toLong(dstSw.getDPID()),
+        				dstPort.getNumber());
+    		
+        		links.add(link);
+        	}
+    	}
+    	
      	return links;
 	}
 	
@@ -222,14 +238,11 @@
 	// TODO: Fix me
 	@Override
 	public void deleteLinksOnPort(Long dpid, short port) {
-		// BEGIN: Trial code
-		// author: Naoki Shiota
 		List<Link> linksToDelete = getLinks(dpid,port);
 		
 		for(Link l : linksToDelete) {
 			deleteLink(l);
 		}
-		// END: Trial code
 	}
 
 	/**
@@ -242,6 +255,23 @@
 	public List<Link> getLinks(String dpid) {
 		List<Link> links = new ArrayList<Link>();
 
+		ISwitchObject srcSw = dbop.searchSwitch(dpid);
+		
+		if(srcSw != null) {
+			for(IPortObject srcPort : srcSw.getPorts()) {
+				for(IPortObject dstPort : srcPort.getLinkedPorts()) {
+					ISwitchObject dstSw = dstPort.getSwitch();
+					if(dstSw != null) {
+		        		Link link = new Link(HexString.toLong(srcSw.getDPID()),
+		        				srcPort.getNumber(),
+		        				HexString.toLong(dstSw.getDPID()),
+		        				dstPort.getNumber());
+		        		links.add(link);
+					}
+				}
+			}
+		}
+		
 		return links;
 	}
 
diff --git a/src/test/java/net/floodlightcontroller/linkdiscovery/internal/LinkStorageImplTest.java b/src/test/java/net/floodlightcontroller/linkdiscovery/internal/LinkStorageImplTest.java
index ba01f3a..a030744 100644
--- a/src/test/java/net/floodlightcontroller/linkdiscovery/internal/LinkStorageImplTest.java
+++ b/src/test/java/net/floodlightcontroller/linkdiscovery/internal/LinkStorageImplTest.java
@@ -176,7 +176,7 @@
 		
 		//Use the link storage API to add the link
 		linkStorage.update(linkToCreate, ILinkStorage.DM_OPERATION.CREATE);
-		doTestLinkIsInGraph(linkToVerify);
+		doTestLinkExist(linkToVerify);
 
 		// Avoiding duplication is out of scope. DBOperation is responsible for this.
 //		// Add same link
@@ -197,7 +197,7 @@
 		
 		//Use the link storage API to add the link
 		linkStorage.update(linkToInsert, ILinkStorage.DM_OPERATION.INSERT);
-		doTestLinkIsInGraph(linkToVerify);
+		doTestLinkExist(linkToVerify);
 	}
 	
 	/**
@@ -210,7 +210,7 @@
 
 		// Test deletion of existing link
 		linkStorage.update(linkToDelete, DM_OPERATION.DELETE);
-		doTestLinkIsNotInGraph(linkToVerify);
+		doTestLinkNotExist(linkToVerify);
 	}
 
 	/**
@@ -224,7 +224,7 @@
 		// Test creation of new links
 		linkStorage.update(linksToCreate, ILinkStorage.DM_OPERATION.CREATE);
 		for(Link l : linksToVerify) {
-			doTestLinkIsInGraph(l);
+			doTestLinkExist(l);
 		}
 	
 		// Out of scope: DBOperation is responsible for avoiding duplication.
@@ -248,8 +248,8 @@
 		
 		// Test creation of mixture of new/existing links
 		linkStorage.update(linksToCreate, ILinkStorage.DM_OPERATION.CREATE);
-		doTestLinkIsInGraph(createFeasibleLink());
-		doTestLinkIsInGraph(createExistingLink());
+		doTestLinkExist(createFeasibleLink());
+		doTestLinkExist(createExistingLink());
 	}
 
 	/**
@@ -263,7 +263,7 @@
 		// Test insertion of new links
 		linkStorage.update(linksToInsert, ILinkStorage.DM_OPERATION.INSERT);
 		for(Link l : linksToVerify) {
-			doTestLinkIsInGraph(l);
+			doTestLinkExist(l);
 		}
 	}
 	
@@ -278,8 +278,8 @@
 		
 		// Test insertion of mixture of new/existing links
 		linkStorage.update(linksToInsert, ILinkStorage.DM_OPERATION.INSERT);
-		doTestLinkIsInGraph(createFeasibleLink());
-		doTestLinkIsInGraph(createExistingLink());
+		doTestLinkExist(createFeasibleLink());
+		doTestLinkExist(createExistingLink());
 	}
 
 	/**
@@ -293,7 +293,7 @@
 		// Test deletion of existing links
 		linkStorage.update(linksToDelete, ILinkStorage.DM_OPERATION.DELETE);
 		for(Link l : linksToVerify) {
-			doTestLinkIsNotInGraph(l);
+			doTestLinkNotExist(l);
 		}
 	}
 	
@@ -308,8 +308,8 @@
 		
 		// Test deletion of mixture of new/existing links
 		linkStorage.update(linksToDelete, ILinkStorage.DM_OPERATION.DELETE);
-		doTestLinkIsNotInGraph(createFeasibleLink());
-		doTestLinkIsNotInGraph(createExistingLink());
+		doTestLinkNotExist(createFeasibleLink());
+		doTestLinkNotExist(createExistingLink());
 	}
 	
 	// TODO: remove @Ignore after UPDATE method is implemented
@@ -338,7 +338,7 @@
 		
 		//Use the link storage API to add the link
 		linkStorage.updateLink(linkToCreate, null, ILinkStorage.DM_OPERATION.CREATE);
-		doTestLinkIsInGraph(linkToVerify);
+		doTestLinkExist(linkToVerify);
 	}
 	
 	/**
@@ -352,7 +352,7 @@
 		//Use the link storage API to add the link
 		linkStorage.updateLink(linkToInsert, null, ILinkStorage.DM_OPERATION.INSERT);
 
-		doTestLinkIsInGraph(linkToVerify);
+		doTestLinkExist(linkToVerify);
 	}
 	
 	// TODO: Check if addOrUpdateLink() should accept DELETE operation. If not, remove this test.
@@ -366,14 +366,14 @@
 
 		// Test deletion of existing link
 		linkStorage.updateLink(linkToDelete, null, DM_OPERATION.DELETE);
-		doTestLinkIsNotInGraph(linkToVerify);
+		doTestLinkNotExist(linkToVerify);
 		
 		linkToDelete = createFeasibleLink();
 		linkToVerify = createFeasibleLink();
 
 		// Test deletion of not-existing link
 		linkStorage.updateLink(linkToDelete, null, DM_OPERATION.DELETE);
-		doTestLinkIsNotInGraph(linkToVerify);
+		doTestLinkNotExist(linkToVerify);
 	}
 	
 	/**
@@ -427,7 +427,7 @@
 		Link linkToVerify = createExistingLink();
 		
 		linkStorage.deleteLink(linkToDelete);
-		doTestLinkIsNotInGraph(linkToVerify);
+		doTestLinkNotExist(linkToVerify);
 	}
 	
 	/**
@@ -440,7 +440,7 @@
 		
 		linkStorage.deleteLinks(linksToDelete);
 		for(Link l : linksToVerify) {
-			doTestLinkIsNotInGraph(l);
+			doTestLinkNotExist(l);
 		}
 	}
 	
@@ -455,8 +455,8 @@
 		
 		// Test deletion of mixture of new/existing links
 		linkStorage.deleteLinks(linksToDelete);
-		doTestLinkIsNotInGraph(createFeasibleLink());
-		doTestLinkIsNotInGraph(createExistingLink());
+		doTestLinkNotExist(createFeasibleLink());
+		doTestLinkNotExist(createExistingLink());
 	}
 
 	/**
@@ -483,14 +483,14 @@
 		
 		linkStorage.deleteLinksOnPort(linkToDelete.getSrc(), linkToDelete.getSrcPort());
 		
-		doTestLinkIsNotInGraph(linkToVerify);
+		doTestLinkNotExist(linkToVerify);
 	}
 
 	/**
-	 * Test if titanGraph has specific link
+	 * Test if specific link is existing
 	 * @param link 
 	 */
-	private void doTestLinkIsInGraph(Link link) {
+	private void doTestLinkExist(Link link) {
 		int count = 0;
 		for(Link lt : links) {
 			if(lt.equals(link)) {
@@ -505,7 +505,7 @@
 	 * Test if titanGraph doesn't have specific link
 	 * @param link
 	 */
-	private void doTestLinkIsNotInGraph(Link link) {
+	private void doTestLinkNotExist(Link link) {
 		assertFalse(links.contains(link));
 	}
 	
@@ -516,6 +516,11 @@
 	private void doTestLinkHasStateOf(Link link, LinkInfo info) {
 	}
 	
+	/**
+	 * Class defines a function called back when IPortObject::removeLink is called.
+	 * @author Naoki Shiota
+	 *
+	 */
 	private class RemoveLinkCallback implements IAnswer<Object> {
 		private long dpid;
 		private short port;
@@ -535,6 +540,11 @@
 		}
 	}
 	
+	/**
+	 * Class defines a function called back when IPortObject::setLinkPort is called.
+	 * @author Naoki Shiota
+	 *
+	 */
 	private class SetLinkPortCallback implements IAnswer<Object> {
 		private long dpid;
 		private short port;
@@ -557,11 +567,11 @@
 	
 	// ------------------------Creation of Mock-----------------------------
 	/**
-	 * Create mock of GraphDBOperation which hooks port-related methods.
-	 * @return
+	 * Create a mock GraphDBOperation which hooks port-related methods.
+	 * @return EasyMock-wrapped GraphDBOperation object.
 	 */
 	private GraphDBOperation createMockGraphDBOperation() {
-		GraphDBOperation mockDBOpe = EasyMock.createMock(GraphDBOperation.class);
+		GraphDBOperation mockDBOpe = EasyMock.createNiceMock(GraphDBOperation.class);
 		
 		// Mock searchPort() method to create new mock IPortObject.
 		EasyMock.expect(mockDBOpe.searchPort((String)EasyMock.anyObject(), EasyMock.anyShort())).
@@ -572,13 +582,12 @@
 				short port = (Short) EasyMock.getCurrentArguments()[1];
 				
 				IPortObject ret = createMockPort(dpid,port);
-				mockToPortInfoMap.put(ret, new PortInfo(dpid,port));
 				
 				return ret;
 			}
 		}).anyTimes();
 		
-		// Mock commit() method to remember "COMMIT" event.
+		// Mock commit() method to commit change of link information
 		mockDBOpe.commit();
 		EasyMock.expectLastCall().andAnswer(new IAnswer<Object>() {
 			@Override
@@ -605,14 +614,21 @@
 				actions.clear();
 				return null;
 			}
-		}).anyTimes();
+		}).atLeastOnce();
 		
 		EasyMock.replay(mockDBOpe);
 		return mockDBOpe;
 	}
 	
+	/**
+	 * Create a mock IPortObject using given DPID and port number.
+	 * IPortObject can't store DPID, so DPID is stored to mockToPortInfoMap for later use.
+	 * @param dpid DPID of a port
+	 * @param number Port Number
+	 * @return EasyMock-wrapped IPortObject
+	 */
 	private IPortObject createMockPort(long dpid, short number) {
-		IPortObject mockPort = EasyMock.createMock(IPortObject.class);
+		IPortObject mockPort = EasyMock.createNiceMock(IPortObject.class);
 		
 		EasyMock.expect(mockPort.getNumber()).andReturn(number);
 		
@@ -639,7 +655,9 @@
 			}
 		}).anyTimes();
 		
+		mockToPortInfoMap.put(mockPort, new PortInfo(dpid,number));
 		EasyMock.replay(mockPort);
+		
 		return mockPort;
 	}
 
diff --git a/src/test/java/net/floodlightcontroller/linkdiscovery/internal/TestGraphDBOperation.java b/src/test/java/net/floodlightcontroller/linkdiscovery/internal/TestGraphDBOperation.java
new file mode 100644
index 0000000..1a239ed
--- /dev/null
+++ b/src/test/java/net/floodlightcontroller/linkdiscovery/internal/TestGraphDBOperation.java
@@ -0,0 +1,670 @@
+package net.floodlightcontroller.linkdiscovery.internal;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.codehaus.jackson.annotate.JsonIgnore;
+import org.codehaus.jackson.annotate.JsonProperty;
+import org.easymock.EasyMock;
+import org.openflow.util.HexString;
+
+import com.tinkerpop.blueprints.Direction;
+import com.tinkerpop.blueprints.Vertex;
+import com.tinkerpop.frames.Adjacency;
+import com.tinkerpop.frames.Incidence;
+import com.tinkerpop.frames.Property;
+import com.tinkerpop.frames.annotations.gremlin.GremlinGroovy;
+import com.tinkerpop.frames.annotations.gremlin.GremlinParam;
+
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IDeviceObject;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IFlowEntry;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IFlowPath;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IPortObject;
+import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.ISwitchObject;
+import net.onrc.onos.ofcontroller.core.ISwitchStorage.SwitchState;
+import net.onrc.onos.ofcontroller.util.FlowEntryId;
+import net.onrc.onos.ofcontroller.util.FlowId;
+import net.onrc.onos.util.GraphDBConnection;
+import net.onrc.onos.util.GraphDBOperation;
+import net.onrc.onos.util.IDBConnection;
+
+public class TestGraphDBOperation extends GraphDBOperation {
+	protected List<TestSwitchObject> switches;
+	protected List<TestPortObject> ports;
+//	protected List<TestDeviceObject> devices;
+//	protected List<TestFlowEntry> flows;
+
+	protected List<TestSwitchObject> switchesToAdd;
+	protected List<TestPortObject> portsToAdd;
+//	protected List<TestDeviceObject> devicesToAdd;
+//	protected List<TestFlowEntry> flowsToAdd;
+
+	protected List<TestSwitchObject> switchesToRemove;
+	protected List<TestPortObject> portsToRemove;
+//	protected List<TestDeviceObject> devicesToRemove;
+//	protected List<TestFlowEntry> flowsToRemove;
+
+
+	// Testable implementations of INetMapTopologyObject interfaces
+	
+	public static class TestSwitchObject implements ISwitchObject {
+		private String state,type,dpid;
+		private List<IPortObject> ports;
+		private List<IDeviceObject> devices;
+		private List<IFlowEntry> flows;
+
+		private String stateToUpdate, typeToUpdate, dpidToUpdate;
+		private List<IPortObject> portsToAdd;
+		private List<IPortObject> portsToRemove;
+
+		public TestSwitchObject() {
+			type = "switch";
+			state = "ACTIVE";
+			
+			ports = new ArrayList<IPortObject>();
+			portsToAdd = new ArrayList<IPortObject>();
+			portsToRemove = new ArrayList<IPortObject>();
+			devices = new ArrayList<IDeviceObject>();
+			flows = new ArrayList<IFlowEntry>();
+			
+			clearUncommitedData();
+		}
+		
+		public void commit() {
+			for(IPortObject port : portsToAdd) {
+				ports.add(port);
+			}
+			for(IPortObject port : portsToRemove) {
+				ports.remove(port);
+			}
+			if(stateToUpdate != null) { state = stateToUpdate; }
+			if(typeToUpdate != null) { type = typeToUpdate; }
+			if(dpidToUpdate != null) { dpid = dpidToUpdate; }
+
+			clearUncommitedData();
+		}
+		
+		public void rollback() {
+			clearUncommitedData();
+		}
+		
+		public void clearUncommitedData() {
+			portsToAdd.clear();
+			portsToRemove.clear();
+			stateToUpdate = typeToUpdate = dpidToUpdate = null;
+		}
+		
+		public void setDpidForTest(String dpid) { this.dpid = dpid; }
+		public void setStateForTest(String state) { this.state = state; }
+		public void setTypeForTest(String type) { this.type = type; }
+		public void addPortForTest(TestPortObject port) { ports.add(port);  }
+		
+		@Override
+		@JsonProperty("state")
+		@Property("state")
+		public String getState() { return state; }
+	
+		@Override
+		@Property("state")
+		public void setState(String state) { this.stateToUpdate = state; }
+	
+		@Override
+		@JsonIgnore
+		@Property("type")
+		public String getType() { return type ; }
+	
+		@Override
+		@Property("type")
+		public void setType(String type) { this.typeToUpdate = type; }
+	
+		// Not support for test
+		@Override
+		public Vertex asVertex() { return null; }
+	
+		@Override
+		@JsonProperty("dpid")
+		@Property("dpid")
+		public String getDPID() { return dpid; }
+	
+		@Override
+		@Property("dpid")
+		public void setDPID(String dpid) { this.dpidToUpdate = dpid; }
+	
+		@Override
+		@JsonProperty("ports")
+		@Adjacency(label = "on")
+		public Iterable<IPortObject> getPorts() { return ports; }
+	
+		@Override
+		@JsonIgnore
+		@GremlinGroovy("_().out('on').has('number',port_num)")
+		public IPortObject getPort(@GremlinParam("port_num") short port_num) {
+			for(IPortObject port : ports) {
+				if(port.getNumber() == port_num) {
+					return port;
+				}
+			}
+			return null;
+		}
+	
+		@Override
+		@Adjacency(label = "on")
+		public void addPort(IPortObject port) { portsToAdd.add(port); }
+	
+		@Override
+		@Adjacency(label = "on")
+		public void removePort(IPortObject port) { portsToRemove.add(port); }
+	
+		@Override
+		@JsonIgnore
+		@GremlinGroovy("_().out('on').out('host')")
+		public Iterable<IDeviceObject> getDevices() { return devices; }
+	
+		@Override
+		@JsonIgnore
+		@Incidence(label = "switch", direction = Direction.IN)
+		public Iterable<IFlowEntry> getFlowEntries() { return flows; }
+	}
+	
+	public static class TestPortObject implements IPortObject {
+		private String state,type,desc;
+		private Short number;
+		private Integer port_state;
+		private ISwitchObject sw;
+		private List<IPortObject> linkedPorts;
+		private List<IDeviceObject> devices;
+		private List<IFlowEntry> flows;
+		
+		private String stateToUpdate,typeToUpdate,descToUpdate;
+		private Short numberToUpdate;
+		private Integer port_stateToUpdate;
+		private List<IPortObject> linkedPortsToAdd;
+		private List<IPortObject> linkedPortsToRemove;
+		
+
+		public TestPortObject() {
+			type = "port";
+			state = "ACTIVE";
+
+			linkedPorts = new ArrayList<IPortObject>();
+			linkedPortsToAdd = new ArrayList<IPortObject>();
+			linkedPortsToRemove = new ArrayList<IPortObject>();
+			devices = new ArrayList<IDeviceObject>();
+			flows = new ArrayList<IFlowEntry>();
+			
+			clearUncommitedData();
+		}
+		
+		public void commit() {
+			for(IPortObject port : linkedPortsToAdd) {
+				linkedPorts.add(port);
+			}
+			for(IPortObject port : linkedPortsToRemove) {
+				linkedPorts.remove(port);
+			}
+			if(stateToUpdate != null) { state = stateToUpdate; }
+			if(typeToUpdate != null) { type = typeToUpdate; }
+			if(descToUpdate != null) { desc = descToUpdate; }
+			if(numberToUpdate != null) { number = numberToUpdate; }
+			if(port_stateToUpdate != null) { port_state = port_stateToUpdate; }
+			
+			clearUncommitedData();
+		}
+		
+		public void rollback() {
+			clearUncommitedData();
+		}
+		
+		public void clearUncommitedData() {
+			linkedPortsToAdd.clear();
+			linkedPortsToRemove.clear();
+			stateToUpdate = typeToUpdate = descToUpdate = null;
+			port_stateToUpdate = null;
+			numberToUpdate = null;
+		}
+		
+		public void setStateForTest(String state) { this.state = state; }
+		public void setTypeForTest(String type) { this.type = type; }
+		public void setDescForTest(String desc) { this.desc = desc; }
+		public void setNumberForTest(Short number) { this.number = number; }
+		public void setPortStateForTest(Integer state) { this.port_state = state; }
+		public void setSwitchForTest(ISwitchObject sw) { this.sw = sw; }
+		public void addLinkedPortForTest(TestPortObject port) { this.linkedPorts.add(port); }
+		
+		@Override
+		@JsonProperty("state")
+		@Property("state")
+		public String getState() { return state; }
+
+		@Override
+		@Property("state")
+		public void setState(String state) { this.stateToUpdate = state; }
+
+		@Override
+		@JsonIgnore
+		@Property("type")
+		public String getType() { return type; }
+
+		@Override
+		@Property("type")
+		public void setType(String type) { this.typeToUpdate = type; }
+
+		// not support for test
+		@Override
+		public Vertex asVertex() {
+			return null;
+		}
+
+		@Override
+		@JsonProperty("number")
+		@Property("number")
+		public Short getNumber() { return number; }
+
+		@Override
+		@Property("number")
+		public void setNumber(Short n) { this.numberToUpdate = n; }
+
+		@Override
+		@JsonProperty("desc")
+		@Property("desc")
+		public String getDesc() { return desc; }
+
+		@Override
+		@Property("desc")
+		public void setDesc(String s) { this.descToUpdate = s; }
+
+		@Override
+		@JsonIgnore
+		@Property("port_state")
+		public Integer getPortState() { return port_state; }
+
+		@Override
+		@Property("port_state")
+		public void setPortState(Integer s) { this.port_stateToUpdate = s; }
+
+		@Override
+		@JsonIgnore
+		@Incidence(label = "on", direction = Direction.IN)
+		public ISwitchObject getSwitch() { return sw; }
+
+		@Override
+		@JsonProperty("devices")
+		@Adjacency(label = "host")
+		public Iterable<IDeviceObject> getDevices() { return devices; }
+
+		@Override
+		@Adjacency(label = "host")
+		public void setDevice(IDeviceObject device) { devices.add(device); }
+
+		@Override
+		@Adjacency(label = "host")
+		public void removeDevice(IDeviceObject device) { devices.remove(device); }
+
+		@Override
+		@JsonIgnore
+		@Incidence(label = "inport", direction = Direction.IN)
+		public Iterable<IFlowEntry> getInFlowEntries() {
+			// TODO Auto-generated method stub
+			return null;
+		}
+
+		@Override
+		@JsonIgnore
+		@Incidence(label = "outport", direction = Direction.IN)
+		public Iterable<IFlowEntry> getOutFlowEntries() {
+			// TODO Auto-generated method stub
+			return null;
+		}
+
+		@Override
+		@JsonIgnore
+		@Adjacency(label = "link")
+		public Iterable<IPortObject> getLinkedPorts() { return linkedPorts; }
+
+		@Override
+		@Adjacency(label = "link")
+		public void removeLink(IPortObject dest_port) { linkedPortsToRemove.add(dest_port); }
+
+		@Override
+		@Adjacency(label = "link")
+		public void setLinkPort(IPortObject dest_port) { linkedPortsToAdd.add(dest_port); }
+	}
+	
+	
+	public TestGraphDBOperation() {
+		super(EasyMock.createNiceMock(GraphDBConnection.class));
+		
+		switches = new ArrayList<TestSwitchObject>();
+		ports = new ArrayList<TestPortObject>();
+//		devices = new ArrayList<TestDeviceObject>();
+//		flows = new ArrayList<TestFlowEntry>();
+		
+		switchesToAdd = new ArrayList<TestSwitchObject>();
+		portsToAdd = new ArrayList<TestPortObject>();
+//		devicesToAdd = new ArrayList<TestDeviceObject>();
+//		flowsToAdd = new ArrayList<TestFlowEntry>();
+
+		switchesToRemove = new ArrayList<TestSwitchObject>();
+		portsToRemove = new ArrayList<TestPortObject>();
+//		devicesToRemove = new ArrayList<TestDeviceObject>();
+//		flowsToRemove = new ArrayList<TestFlowEntry>();
+		
+		clear();
+	}
+	
+	private void clear() {
+		for(TestSwitchObject sw : switches) {
+			sw.clearUncommitedData();
+		}
+		for(TestSwitchObject sw : switchesToAdd) {
+			sw.clearUncommitedData();
+		}
+		
+		for(TestPortObject port : ports) {
+			port.clearUncommitedData();
+		}
+		for(TestPortObject port : portsToAdd) {
+			port.clearUncommitedData();
+		}
+		
+		switchesToAdd.clear();
+		switchesToRemove.clear();
+		portsToAdd.clear();
+		portsToRemove.clear();
+	}
+	
+	
+	// this.*ForTest() methods below are supposed to be used for creation of test topology.
+	/**
+	 * 
+	 * @param dpid
+	 * @return
+	 */
+	public TestSwitchObject createNewSwitchForTest(String dpid) {
+		for(TestSwitchObject sw_loop : switches) {
+			if(sw_loop.getDPID().equals(dpid)) {
+				// Already created
+				return sw_loop;
+			}
+		}
+
+		TestSwitchObject sw = new TestSwitchObject();
+		
+		sw.setDpidForTest(dpid);
+		switches.add(sw);
+		
+		return sw;
+	}
+	
+	public TestPortObject createNewPortForTest(String dpid, Short number) {
+		TestSwitchObject sw = null;
+		
+		for(TestSwitchObject sw_loop : switches) {
+			if(sw_loop.getDPID().equals(dpid)) {
+				sw = sw_loop;
+			}
+		}
+		
+		if(sw != null) {
+			TestPortObject port = new TestPortObject();
+			port.setNumberForTest(number);
+			port.setSwitchForTest(sw);
+
+			return port;
+		} else {
+			return  null;
+		}
+	}
+	
+	public void setLinkBetweenPortsForTest(TestPortObject src, TestPortObject dst) {
+		src.addLinkedPortForTest(dst);
+		//dst.addLinkedPortForTest(src);
+	}
+
+	// Overriding methods below are to mock GraphDBOperation class.
+	@Override
+	public ISwitchObject newSwitch(String dpid) {
+		TestSwitchObject sw = new TestSwitchObject();
+		switchesToAdd.add(sw);
+		
+		return sw;
+	}
+
+	@Override
+	public ISwitchObject searchSwitch(String dpid) {
+		for(ISwitchObject sw : switches) {
+			if(sw.getDPID().equals(dpid)) {
+				return sw;
+			}
+		}
+		return null;
+	}
+
+	@Override
+	public ISwitchObject searchActiveSwitch(String dpid) {
+		for(ISwitchObject sw : switches) {
+			if(sw.getDPID().equals(dpid) && sw.getState().equals("ACTIVE")) {
+				return sw;
+			}
+		}
+		return null;
+	}
+
+	@Override
+	public Iterable<ISwitchObject> getActiveSwitches() {
+		List<ISwitchObject> list = new ArrayList<ISwitchObject>();
+		
+		for(ISwitchObject sw : switches) {
+			if(sw.getState().equals("ACTIVE")) {
+				list.add(sw);
+			}
+		}
+		return list.isEmpty() ? null : list;
+	}
+
+	@Override
+	public Iterable<ISwitchObject> getAllSwitches() {
+		List<ISwitchObject> list = new ArrayList<ISwitchObject>();
+		
+		for(ISwitchObject sw : switches) {
+			list.add(sw);
+		}
+		
+		return list.isEmpty() ? null : list;
+	}
+
+	@Override
+	public Iterable<ISwitchObject> getInactiveSwitches() {
+		List<ISwitchObject> list = new ArrayList<ISwitchObject>();
+		
+		for(ISwitchObject sw : switches) {
+			if(! sw.getState().equals("ACTIVE")) {
+				list.add(sw);
+			}
+		}
+		return list.isEmpty() ? null : list;
+	}
+
+	@Override
+	public Iterable<IFlowEntry> getAllSwitchNotUpdatedFlowEntries() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public void removeSwitch(ISwitchObject sw) {
+		if(switches.contains(sw)) {
+			switchesToRemove.add((TestSwitchObject)sw);
+		}
+	}
+
+	@Override
+	public IPortObject newPort(Short portNumber) {
+		TestPortObject port = new TestPortObject();
+		port.setNumber(portNumber);
+		
+		return port;
+	}
+
+	public IPortObject newPort(Long dpid, Short portNumber) {
+		TestPortObject port = null;
+		TestSwitchObject sw = (TestSwitchObject)searchSwitch(HexString.toHexString(dpid));
+		
+		if(sw != null) {
+			port = (TestPortObject)newPort(portNumber);
+			portsToAdd.add(port);
+			sw.addPort(port);
+		}
+		
+		return port;
+	}
+	
+	@Override
+	public IPortObject searchPort(String dpid_str, short number) {
+		for(TestSwitchObject sw : switches) {
+			if(sw.getDPID().equals(dpid_str)) {
+				for(IPortObject port : sw.getPorts()) {
+					if(port.getNumber().equals(number)) {
+						return port;
+					}
+				}
+			}
+		}
+		return null;
+	}
+
+	@Override
+	public void removePort(IPortObject port) {
+		for(TestSwitchObject sw : switches) {
+			for(IPortObject pt : sw.getPorts()) {
+				if(pt.equals(port)) {
+					sw.removePort(port);
+				}
+			}
+		}
+		portsToRemove.add((TestPortObject)port);
+	}
+
+	@Override
+	public IDeviceObject newDevice() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public IDeviceObject searchDevice(String macAddr) {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public Iterable<IDeviceObject> getDevices() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public void removeDevice(IDeviceObject dev) {
+		// TODO Auto-generated method stub
+
+	}
+
+	@Override
+	public IFlowPath newFlowPath() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public IFlowPath searchFlowPath(FlowId flowId) {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public IFlowPath getFlowPathByFlowEntry(IFlowEntry flowEntry) {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public Iterable<IFlowPath> getAllFlowPaths() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public void removeFlowPath(IFlowPath flowPath) {
+		// TODO Auto-generated method stub
+
+	}
+
+	@Override
+	public IFlowEntry newFlowEntry() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public IFlowEntry searchFlowEntry(FlowEntryId flowEntryId) {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public Iterable<IFlowEntry> getAllFlowEntries() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public void removeFlowEntry(IFlowEntry flowEntry) {
+		// TODO Auto-generated method stub
+
+	}
+
+	@Override
+	public IDBConnection getDBConnection() {
+		return super.getDBConnection();
+	}
+
+	@Override
+	public void commit() {
+		for(TestSwitchObject sw : switchesToAdd) {
+			switches.add(sw);
+		}
+		for(TestSwitchObject sw : switchesToRemove) {
+			sw.commit();
+			switches.remove(sw);
+		}
+		for(TestSwitchObject sw : switches) {
+			sw.commit();
+		}
+		
+		for(TestPortObject port : portsToAdd) {
+			ports.add(port);
+		}
+		for(TestPortObject port : portsToRemove) {
+			port.commit();
+			ports.remove(port);
+		}
+		for(TestPortObject port : ports) {
+			port.commit();
+		}
+		
+		clear();
+	}
+
+	@Override
+	public void rollback() {
+		clear();
+	}
+
+	@Override
+	public void close() {
+		// TODO Auto-generated method stub
+
+	}
+}