diff --git a/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/dataflow/io/NodeSequenceWriterFactory.java b/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/dataflow/io/NodeSequenceWriterFactory.java
index df4c08b..7c70aa9 100644
--- a/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/dataflow/io/NodeSequenceWriterFactory.java
+++ b/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/dataflow/io/NodeSequenceWriterFactory.java
@@ -4,6 +4,7 @@
 import java.io.IOException;
 
 import org.apache.hadoop.fs.FSDataOutputStream;
+import org.apache.hadoop.io.NullWritable;
 import org.apache.hadoop.io.SequenceFile;
 import org.apache.hadoop.io.SequenceFile.CompressionType;
 import org.apache.hadoop.io.SequenceFile.Writer;
@@ -56,7 +57,7 @@
         @Override
         public void open(DataOutput output) throws HyracksDataException {
             try {
-                writer = SequenceFile.createWriter(cf.getConf(), (FSDataOutputStream) output, NodeWritable.class, null,
+                writer = SequenceFile.createWriter(cf.getConf(), (FSDataOutputStream) output, NodeWritable.class, NullWritable.class,
                         CompressionType.NONE, null);
             } catch (IOException e) {
                 throw new HyracksDataException(e);
@@ -78,7 +79,7 @@
                     tuple.getFieldData(InputKmerBytesField), tuple.getFieldStart(InputKmerBytesField));
 
             try {
-                writer.append(node, null);
+                writer.append(node, NullWritable.get());
             } catch (IOException e) {
                 throw new HyracksDataException(e);
             }
@@ -86,8 +87,6 @@
 
         @Override
         public void close(DataOutput output) throws HyracksDataException {
-            // TODO Auto-generated method stub
-
         }
 
     }
diff --git a/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/job/JobGenGroupbyReadID.java b/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/job/JobGenGroupbyReadID.java
index 06fcd8e..fb0a3de 100644
--- a/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/job/JobGenGroupbyReadID.java
+++ b/genomix/genomix-hyracks/src/main/java/edu/uci/ics/genomix/hyracks/job/JobGenGroupbyReadID.java
@@ -108,9 +108,9 @@
                                             fieldOffset += kmer.getLength();
 
                                             output.write(Integer.toString(i - 1).getBytes());
-                                            output.writeByte(' ');
+                                            output.writeByte('\t');
                                             output.write(plist.toString().getBytes());
-                                            output.writeByte(' ');
+                                            output.writeByte('\t');
                                             output.write(kmer.toString().getBytes());
                                             output.writeByte('\t');
                                         }
diff --git a/genomix/genomix-hyracks/src/test/java/edu/uci/ics/genomix/hyracks/test/JobRunStepByStepTest.java b/genomix/genomix-hyracks/src/test/java/edu/uci/ics/genomix/hyracks/test/JobRunStepByStepTest.java
index 8451567..df25fd7 100644
--- a/genomix/genomix-hyracks/src/test/java/edu/uci/ics/genomix/hyracks/test/JobRunStepByStepTest.java
+++ b/genomix/genomix-hyracks/src/test/java/edu/uci/ics/genomix/hyracks/test/JobRunStepByStepTest.java
@@ -15,6 +15,7 @@
 import org.apache.hadoop.fs.FileUtil;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.io.NullWritable;
 import org.apache.hadoop.io.SequenceFile;
 import org.apache.hadoop.mapred.FileInputFormat;
 import org.apache.hadoop.mapred.FileOutputFormat;
@@ -26,7 +27,7 @@
 import edu.uci.ics.genomix.hyracks.driver.Driver;
 import edu.uci.ics.genomix.hyracks.driver.Driver.Plan;
 import edu.uci.ics.genomix.hyracks.job.GenomixJobConf;
-import edu.uci.ics.genomix.type.KmerBytesWritable;
+import edu.uci.ics.genomix.type.NodeWritable;
 
 @SuppressWarnings("deprecation")
 public class JobRunStepByStepTest {
@@ -93,11 +94,12 @@
         conf.set(GenomixJobConf.OUTPUT_FORMAT, GenomixJobConf.OUTPUT_FORMAT_TEXT);
         conf.set(GenomixJobConf.GROUPBY_TYPE, GenomixJobConf.GROUPBY_TYPE_PRECLUSTER);
         driver.runJob(new GenomixJobConf(conf), Plan.OUTPUT_GROUPBY_READID, true);
-        Assert.assertEquals(true, checkResults(EXPECTED_GROUPBYREADID, new int [] {2}));
+        Assert.assertEquals(true, checkResults(EXPECTED_GROUPBYREADID, new int [] {2,5,8,11}));
     }
 
     public void TestEndToEnd() throws Exception {
-        conf.set(GenomixJobConf.OUTPUT_FORMAT, GenomixJobConf.OUTPUT_FORMAT_TEXT);
+        //conf.set(GenomixJobConf.OUTPUT_FORMAT, GenomixJobConf.OUTPUT_FORMAT_TEXT);
+        conf.set(GenomixJobConf.OUTPUT_FORMAT, GenomixJobConf.OUTPUT_FORMAT_BINARY);
         cleanUpReEntry();
         conf.set(GenomixJobConf.GROUPBY_TYPE, GenomixJobConf.GROUPBY_TYPE_PRECLUSTER);
         driver.runJob(new GenomixJobConf(conf), Plan.BUILD_DEBRUJIN_GRAPH, true);
@@ -187,18 +189,14 @@
                 }
                 SequenceFile.Reader reader = new SequenceFile.Reader(dfs, path, conf);
 
-                // KmerBytesWritable key = (KmerBytesWritable)
-                // ReflectionUtils.newInstance(reader.getKeyClass(), conf);
-                KmerBytesWritable key = new KmerBytesWritable(conf.getInt(GenomixJobConf.KMER_LENGTH, KmerSize));
-                // KmerCountValue value = (KmerCountValue)
-                // ReflectionUtils.newInstance(reader.getValueClass(), conf);
-                KmerBytesWritable value = null;
-                while (reader.next(key, value)) {
-                    if (key == null || value == null) {
+                NodeWritable node = new NodeWritable(conf.getInt(GenomixJobConf.KMER_LENGTH, KmerSize));
+                NullWritable value = NullWritable.get();
+                while (reader.next(node, value)) {
+                    if (node == null) {
                         break;
                     }
-                    bw.write(key.toString() + "\t" + value.toString());
-                    System.out.println(key.toString() + "\t" + value.toString());
+                    bw.write(node.toString() );
+                    System.out.println(node.toString());
                     bw.newLine();
                 }
                 reader.close();
diff --git a/genomix/genomix-hyracks/src/test/java/edu/uci/ics/genomix/hyracks/test/TestUtils.java b/genomix/genomix-hyracks/src/test/java/edu/uci/ics/genomix/hyracks/test/TestUtils.java
index 6e6a504..d22bd0c 100644
--- a/genomix/genomix-hyracks/src/test/java/edu/uci/ics/genomix/hyracks/test/TestUtils.java
+++ b/genomix/genomix-hyracks/src/test/java/edu/uci/ics/genomix/hyracks/test/TestUtils.java
@@ -164,6 +164,9 @@
     }
     
     private static boolean containStrings(String lineExpected, String actualLine, int[] poslistField) {
+//        if (lineExpected.equals(actualLine)){
+//            return true;
+//        }
         String[] fieldsExp = lineExpected.split("\\\t");
         String[] fieldsAct = actualLine.split("\\\t");
         if (fieldsAct.length != fieldsExp.length) {
diff --git a/genomix/genomix-hyracks/src/test/resources/expected/result_after_readIDAggreage b/genomix/genomix-hyracks/src/test/resources/expected/result_after_readIDAggreage
index 1cd4274..7d2e065 100644
--- a/genomix/genomix-hyracks/src/test/resources/expected/result_after_readIDAggreage
+++ b/genomix/genomix-hyracks/src/test/resources/expected/result_after_readIDAggreage
@@ -1,6 +1,6 @@
-1	0 [] AATAG	1 [] ATAGA	2 [] TAGAA	3 [(6,0)] AGAAG	
-2	0 [] AATAG	1 [] ATAGA	2 [] TAGAA	3 [(6,0)] AGAAG	
-3	0 [] AATAG	1 [] ATAGA	2 [] TAGAA	3 [(6,0)] AGAAG	
-4	0 [] AATAG	1 [] ATAGA	2 [] TAGAA	3 [(6,0)] AGAAG	
-5	0 [] AATAG	1 [] ATAGA	2 [] TAGAA	3 [(6,0)] AGAAG	
-6	0 [(1,3),(2,3),(3,3),(5,3),(4,3)] AGAAG	1 [] GAAGA	2 [] AAGAA	3 [] AGAAG	
+1	0	[]	AATAG	1	[]	ATAGA	2	[]	TAGAA	3	[(6,0)]	AGAAG	
+2	0	[]	AATAG	1	[]	ATAGA	2	[]	TAGAA	3	[(6,0)]	AGAAG	
+3	0	[]	AATAG	1	[]	ATAGA	2	[]	TAGAA	3	[(6,0)]	AGAAG	
+4	0	[]	AATAG	1	[]	ATAGA	2	[]	TAGAA	3	[(6,0)]	AGAAG	
+5	0	[]	AATAG	1	[]	ATAGA	2	[]	TAGAA	3	[(6,0)]	AGAAG	
+6	0	[(1,3),(2,3),(3,3),(5,3),(4,3)]	AGAAG	1	[]	GAAGA	2	[]	AAGAA	3	[]	AGAAG