diff --git a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/KmerBytesWritable.java b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/KmerBytesWritable.java
index 736dc56..d3f47cf 100644
--- a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/KmerBytesWritable.java
+++ b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/KmerBytesWritable.java
@@ -50,6 +50,10 @@
     public KmerBytesWritable(int k, byte[] storage, int offset) {
         setNewReference(k, storage, offset);
     }
+    
+    public KmerBytesWritable(int k, String kmer) {
+        setNewReference(kmer.length(), kmer.getBytes(), 0);
+    }
 
     /**
      * Initial Kmer space by kmerlength
diff --git a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java
index 844e2e8..5d6c36a 100644
--- a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java
+++ b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java
@@ -24,7 +24,7 @@
     }
 
     public NodeWritable(int kmerSize) {
-        nodeID = new PositionWritable(0,(byte) 0);
+        nodeID = new PositionWritable(0, (byte) 0);
         forwardForwardList = new PositionListWritable();
         forwardReverseList = new PositionListWritable();
         reverseForwardList = new PositionListWritable();
@@ -32,6 +32,17 @@
         kmer = new KmerBytesWritable(kmerSize);
     }
 
+    public NodeWritable(PositionWritable nodeID, PositionListWritable FFList, PositionListWritable FRList,
+            PositionListWritable RFList, PositionListWritable RRList, KmerBytesWritable kmer) {
+        this(kmer.getKmerLength());
+        this.nodeID.set(nodeID);
+        forwardForwardList.set(FFList);
+        forwardReverseList.set(FRList);
+        reverseForwardList.set(RFList);
+        reverseReverseList.set(RRList);
+        kmer.set(kmer);
+    }
+
     public void setNodeID(PositionWritable ref) {
         this.setNodeID(ref.getReadID(), ref.getPosInRead());
     }
@@ -43,7 +54,7 @@
     public void setKmer(KmerBytesWritable right) {
         this.kmer.set(right);
     }
-    
+
     public void reset(int kmerSize) {
         nodeID.set(0, (byte) 0);
         forwardForwardList.reset();
@@ -56,7 +67,7 @@
     public PositionListWritable getFFList() {
         return forwardForwardList;
     }
-    
+
     public PositionListWritable getFRList() {
         return forwardReverseList;
     }
@@ -64,7 +75,7 @@
     public PositionListWritable getRFList() {
         return reverseForwardList;
     }
-    
+
     public PositionListWritable getRRList() {
         return reverseReverseList;
     }
@@ -86,8 +97,8 @@
         this.forwardReverseList.set(nextNode.forwardReverseList);
         kmer.mergeNextKmer(initialKmerSize, nextNode.getKmer());
     }
-    
-    public void mergeForwardPre(NodeWritable preNode, int initialKmerSize){
+
+    public void mergeForwardPre(NodeWritable preNode, int initialKmerSize) {
         this.reverseForwardList.set(preNode.reverseForwardList);
         this.reverseReverseList.set(preNode.reverseReverseList);
         kmer.mergePreKmer(initialKmerSize, preNode.getKmer());
@@ -133,6 +144,18 @@
     }
 
     @Override
+    public boolean equals(Object o) {
+        if (o instanceof NodeWritable) {
+            NodeWritable nw = (NodeWritable) o;
+            return (this.nodeID.equals(nw.nodeID) && this.forwardForwardList.equals(nw.forwardForwardList)
+                    && this.forwardReverseList.equals(nw.forwardReverseList)
+                    && this.reverseForwardList.equals(nw.reverseForwardList)
+                    && this.reverseReverseList.equals(nw.reverseReverseList) && this.kmer.equals(nw.kmer));
+        }
+        return false;
+    }
+
+    @Override
     public String toString() {
         StringBuilder sbuilder = new StringBuilder();
         sbuilder.append('(');
@@ -144,15 +167,15 @@
         sbuilder.append(kmer.toString()).append(')');
         return sbuilder.toString();
     }
-    
-    public int inDegree(){
+
+    public int inDegree() {
         return reverseReverseList.getCountOfPosition() + reverseForwardList.getCountOfPosition();
     }
-    
-    public int outDegree(){
+
+    public int outDegree() {
         return forwardForwardList.getCountOfPosition() + forwardReverseList.getCountOfPosition();
     }
-    
+
     /*
      * Return if this node is a "path" compressible node, that is, it has an in-degree and out-degree of 1 
      */
diff --git a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionListWritable.java b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionListWritable.java
index 34fb0f6..cd9fc66 100644
--- a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionListWritable.java
+++ b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionListWritable.java
@@ -4,7 +4,9 @@
 import java.io.DataOutput;
 import java.io.IOException;
 import java.io.Serializable;
+import java.util.Arrays;
 import java.util.Iterator;
+import java.util.List;
 
 import org.apache.hadoop.io.Writable;
 
@@ -32,6 +34,13 @@
     public PositionListWritable(int count, byte[] data, int offset) {
         setNewReference(count, data, offset);
     }
+    
+    public PositionListWritable(List<PositionWritable> posns) {
+        this();
+        for (PositionWritable p : posns) {
+            append(p);
+        }
+    }
 
     public void setNewReference(int count, byte[] data, int offset) {
         this.valueCount = count;
@@ -184,4 +193,23 @@
         }
         return sbuilder.toString();
     }
+    
+    @Override
+    public int hashCode() {
+        return Marshal.hashBytes(getByteArray(), getStartOffset(), getLength());
+    }
+    
+    @Override
+    public boolean equals(Object o) {
+        if (!(o instanceof PositionListWritable))
+            return false;
+        PositionListWritable other = (PositionListWritable) o;
+        if (this.valueCount != other.valueCount)
+            return false;
+        for (int i=0; i < this.valueCount; i++) {
+                if (!this.getPosition(i).equals(other.getPosition(i)))
+                    return false;
+        }
+        return true;
+    }
 }
diff --git a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionWritable.java b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionWritable.java
index 0988813..b548934 100644
--- a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionWritable.java
+++ b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionWritable.java
@@ -132,7 +132,6 @@
                 return diff2;
             }
             return diff1;
-            //            return compareBytes(b1, s1, l1, b2, s2, l2);
         }
     }
 
diff --git a/genomix/genomix-hadoop/pom.xml b/genomix/genomix-hadoop/pom.xml
index 610092a..8ca2fa3 100755
--- a/genomix/genomix-hadoop/pom.xml
+++ b/genomix/genomix-hadoop/pom.xml
@@ -174,5 +174,11 @@
 			<type>test-jar</type>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.apache.mrunit</groupId>
+			<artifactId>mrunit</artifactId>
+			<version>1.0.0</version>
+			<classifier>hadoop1</classifier>
+		</dependency>
 	</dependencies>
 </project>
diff --git a/genomix/genomix-hadoop/src/main/java/edu/uci/ics/genomix/hadoop/velvetgraphbuilding/GraphBuildingDriver.java b/genomix/genomix-hadoop/src/main/java/edu/uci/ics/genomix/hadoop/velvetgraphbuilding/GraphBuildingDriver.java
index eaf2a6f..c735a0d 100644
--- a/genomix/genomix-hadoop/src/main/java/edu/uci/ics/genomix/hadoop/velvetgraphbuilding/GraphBuildingDriver.java
+++ b/genomix/genomix-hadoop/src/main/java/edu/uci/ics/genomix/hadoop/velvetgraphbuilding/GraphBuildingDriver.java
@@ -52,6 +52,7 @@
     public void run(String inputPath, String outputPath, int numReducers, int sizeKmer, int readLength,
             boolean onlyTest1stJob, boolean seqOutput, String defaultConfPath) throws IOException {
         if (onlyTest1stJob == true) {
+            
             runfirstjob(inputPath, numReducers, sizeKmer, readLength, seqOutput, defaultConfPath);
         } else {
             runfirstjob(inputPath, numReducers, sizeKmer, readLength, true, defaultConfPath);
@@ -113,6 +114,7 @@
 
         conf.setPartitionerClass(ReadIDPartitioner.class);
 
+        // grouping is done on the readID only; sorting is based on the (readID, abs(posn)) 
         conf.setOutputKeyComparatorClass(PositionWritable.Comparator.class);
         conf.setOutputValueGroupingComparator(PositionWritable.FirstComparator.class);