diff --git a/public/java/test/org/broadinstitute/sting/utils/pileup/FragmentPileupUnitTest.java b/public/java/test/org/broadinstitute/sting/utils/pileup/FragmentPileupUnitTest.java
new file mode 100644
index 000000000..778259528
--- /dev/null
+++ b/public/java/test/org/broadinstitute/sting/utils/pileup/FragmentPileupUnitTest.java
@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2011, The Broad Institute
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following
+ * conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package org.broadinstitute.sting.utils.pileup;
+
+import net.sf.samtools.SAMFileHeader;
+import net.sf.samtools.SAMReadGroupRecord;
+import net.sf.samtools.SAMRecord;
+import org.broadinstitute.sting.BaseTest;
+import org.broadinstitute.sting.utils.collections.Pair;
+import org.broadinstitute.sting.utils.sam.ArtificialSAMUtils;
+import org.testng.Assert;
+import org.testng.annotations.BeforeTest;
+import org.testng.annotations.DataProvider;
+import org.testng.annotations.Test;
+
+import java.util.*;
+
+/**
+ * Test routines for read-backed pileup.
+ */
+public class FragmentPileupUnitTest extends BaseTest {
+    private static SAMFileHeader header;
+
+    private class FragmentPileupTest extends TestDataProvider {
+        List<TestState> states = new ArrayList<TestState>();
+
+        private FragmentPileupTest(String name, int readLen, int leftStart, int rightStart, boolean leftIsFirst, boolean leftIsNegative) {
+            super(FragmentPileupTest.class, String.format("%s-leftIsFirst:%b-leftIsNegative:%b", name, leftIsFirst, leftIsNegative));
+
+            for ( int pos = leftStart; pos < rightStart + readLen; pos++) {
+                SAMRecord left = ArtificialSAMUtils.createArtificialRead(header, "readpair", 0, leftStart, readLen);
+                SAMRecord right = ArtificialSAMUtils.createArtificialRead(header, "readpair", 0, rightStart, readLen);
+
+                left.setProperPairFlag(true);
+                right.setProperPairFlag(true);
+
+                left.setFirstOfPairFlag(leftIsFirst);
+                right.setFirstOfPairFlag(! leftIsFirst);
+
+                left.setReadNegativeStrandFlag(leftIsNegative);
+                left.setMateNegativeStrandFlag(!leftIsNegative);
+                right.setReadNegativeStrandFlag(!leftIsNegative);
+                right.setMateNegativeStrandFlag(leftIsNegative);
+
+                left.setMateAlignmentStart(right.getAlignmentStart());
+                right.setMateAlignmentStart(left.getAlignmentStart());
+
+                left.setMateReferenceIndex(0);
+                right.setMateReferenceIndex(0);
+
+                int isize = rightStart + readLen - leftStart;
+                left.setInferredInsertSize(isize);
+                right.setInferredInsertSize(-isize);
+
+                boolean posCoveredByLeft = pos >= left.getAlignmentStart() && pos <= left.getAlignmentEnd();
+                boolean posCoveredByRight = pos >= right.getAlignmentStart() && pos <= right.getAlignmentEnd();
+
+                if ( posCoveredByLeft || posCoveredByRight ) {
+                    List<SAMRecord> reads = new ArrayList<SAMRecord>();
+                    List<Integer> offsets = new ArrayList<Integer>();
+
+                    if ( posCoveredByLeft ) {
+                        reads.add(left);
+                        offsets.add(pos - left.getAlignmentStart());
+                    }
+
+                    if ( posCoveredByRight ) {
+                        reads.add(right);
+                        offsets.add(pos - right.getAlignmentStart());
+                    }
+
+                    boolean shouldBeFragment = posCoveredByLeft && posCoveredByRight;
+                    ReadBackedPileup pileup = new ReadBackedPileupImpl(null, reads, offsets);
+                    TestState testState = new TestState(shouldBeFragment, pileup);
+                    states.add(testState);
+                }
+            }
+        }
+    }
+
+    private class TestState {
+        boolean shouldBeFragment;
+        ReadBackedPileup pileup;
+
+        private TestState(final boolean shouldBeFragment, final ReadBackedPileup pileup) {
+            this.shouldBeFragment = shouldBeFragment;
+            this.pileup = pileup;
+        }
+    }
+
+    @DataProvider(name = "fragmentPileupTest")
+    public Object[][] createTests() {
+        for ( boolean leftIsFirst : Arrays.asList(true, false) ) {
+            for ( boolean leftIsNegative : Arrays.asList(true, false) ) {
+                // Overlapping pair
+                // ---->        [first]
+                //   <---       [second]
+                new FragmentPileupTest("overlapping-pair", 10, 1, 5, leftIsFirst, leftIsNegative);
+
+                // Non-overlapping pair
+                // ---->
+                //          <----
+                new FragmentPileupTest("nonoverlapping-pair", 10, 1, 15, leftIsFirst, leftIsNegative);
+            }
+        }
+
+        return FragmentPileupTest.getTests(FragmentPileupTest.class);
+    }
+
+    @Test(enabled = true, dataProvider = "fragmentPileupTest")
+    public void testMe(FragmentPileupTest test) {
+        for ( TestState testState : test.states ) {
+            ReadBackedPileup rbp = testState.pileup;
+            FragmentPileup fp = new FragmentPileup(rbp);
+            Assert.assertEquals(fp.getTwoReadPileup().size(), testState.shouldBeFragment ? 1 : 0);
+            Assert.assertEquals(fp.getOneReadPileup().size(), testState.shouldBeFragment ? 0 : 1);
+        }
+    }
+
+
+    @BeforeTest
+    public void setup() {
+        header = ArtificialSAMUtils.createArtificialSamHeader(1,1,1000);
+    }
+}