diff --git a/public/java/test/org/broadinstitute/sting/gatk/traversals/TraverseActiveRegionsTest.java b/public/java/test/org/broadinstitute/sting/gatk/traversals/TraverseActiveRegionsTest.java
index d61da5a83..ce4d400b4 100644
--- a/public/java/test/org/broadinstitute/sting/gatk/traversals/TraverseActiveRegionsTest.java
+++ b/public/java/test/org/broadinstitute/sting/gatk/traversals/TraverseActiveRegionsTest.java
@@ -28,20 +28,23 @@ import org.testng.annotations.Test;
 
 import java.io.File;
 import java.io.FileNotFoundException;
-import java.util.ArrayList;
-import java.util.List;
+import java.util.*;
 
 /**
  * Created with IntelliJ IDEA.
  * User: thibault
  * Date: 11/13/12
  * Time: 2:47 PM
+ *
+ * Test the Active Region Traversal Contract
+ * http://iwww.broadinstitute.org/gsa/wiki/index.php/Active_Region_Traversal_Contract
  */
 public class TraverseActiveRegionsTest extends BaseTest {
 
     private class DummyActiveRegionWalker extends ActiveRegionWalker<Integer, Integer> {
         private final double prob;
         public List<GenomeLoc> isActiveCalls = new ArrayList<GenomeLoc>();
+        public List<ActiveRegion> mappedActiveRegions = new ArrayList<ActiveRegion>();
 
         public DummyActiveRegionWalker() {
             this.prob = 1.0;
@@ -55,6 +58,7 @@ public class TraverseActiveRegionsTest extends BaseTest {
 
         @Override
         public Integer map(ActiveRegion activeRegion, RefMetaDataTracker metaDataTracker) {
+            mappedActiveRegions.add(activeRegion);
             return 0;
         }
 
@@ -73,7 +77,6 @@ public class TraverseActiveRegionsTest extends BaseTest {
 
     private IndexedFastaSequenceFile reference;
     private GenomeLocParser genomeLocParser;
-    private DummyActiveRegionWalker walker;
 
     @BeforeClass
     private void init() throws FileNotFoundException {
@@ -83,61 +86,133 @@ public class TraverseActiveRegionsTest extends BaseTest {
     }
 
     @Test
-    public void testAllBasesSeenSuite() {
+    public void testAllBasesSeen() {
+        DummyActiveRegionWalker walker = new DummyActiveRegionWalker();
         List<GenomeLoc> intervals = new ArrayList<GenomeLoc>();
-        List<GenomeLoc> activeIntervals = new ArrayList<GenomeLoc>();
 
-        GenomeLoc interval = genomeLocParser.createGenomeLoc("1", 1, 1);
-        intervals.add(interval);
-        testAllBasesSeen(intervals);
+        intervals.add(genomeLocParser.createGenomeLoc("1", 1, 1));
+        List<GenomeLoc> activeIntervals = getIsActiveIntervals(walker, intervals);
+        // Contract: Every genome position in the analysis interval(s) is processed by the walker's isActive() call
+        verifyEqualIntervals(intervals, activeIntervals);
 
-        interval = genomeLocParser.createGenomeLoc("1", 10, 20);
-        intervals.add(interval);
-        testAllBasesSeen(intervals);
+        intervals.add(genomeLocParser.createGenomeLoc("1", 10, 20));
+        activeIntervals = getIsActiveIntervals(walker, intervals);
+        // Contract: Every genome position in the analysis interval(s) is processed by the walker's isActive() call
+        verifyEqualIntervals(intervals, activeIntervals);
+
+        // TODO: more tests and edge cases
     }
 
-    public void testAllBasesSeen(List<GenomeLoc> intervals) {
+    private List<GenomeLoc> getIsActiveIntervals(DummyActiveRegionWalker walker, List<GenomeLoc> intervals) {
         List<GenomeLoc> activeIntervals = new ArrayList<GenomeLoc>();
         for (LocusShardDataProvider dataProvider : createDataProviders(intervals)) {
             t.traverse(walker, dataProvider, 0);
             activeIntervals.addAll(walker.isActiveCalls);
         }
 
-        boolean allBasesSeen = true;
-        for (GenomeLoc base : toBases(intervals)) {
-            boolean thisBaseSeen = false;
-            for (GenomeLoc activeLoc : activeIntervals) {
-                if (base.equals(activeLoc)) {
-                    thisBaseSeen = true;
-                    break;
-                }
-            }
-            if (!thisBaseSeen) {
-                allBasesSeen = false;
-                break;
-            }
-        }
-
-        Assert.assertTrue(allBasesSeen, "Some intervals missing from activity profile");
+        return activeIntervals;
     }
 
-    private List<GenomeLoc> toBases(List<GenomeLoc> intervals) {
-        List<GenomeLoc> bases = new ArrayList<GenomeLoc>();
+    @Test
+    public void testActiveRegionCoverage() {
+        DummyActiveRegionWalker walker = new DummyActiveRegionWalker();
+        List<GenomeLoc> intervals = new ArrayList<GenomeLoc>();
+
+        intervals.add(genomeLocParser.createGenomeLoc("1", 1, 999));
+        intervals.add(genomeLocParser.createGenomeLoc("1", 1000, 1999));
+        intervals.add(genomeLocParser.createGenomeLoc("1", 2000, 2999));
+
+        List<ActiveRegion> activeRegions = getActiveRegions(walker, intervals);
+        verifyActiveRegionCoverage(intervals, activeRegions);
+
+        // TODO: more tests and edge cases
+    }
+
+    private void verifyActiveRegionCoverage(List<GenomeLoc> intervals, List<ActiveRegion> activeRegions) {
+        List<GenomeLoc> intervalStarts = new ArrayList<GenomeLoc>();
+        List<GenomeLoc> intervalStops = new ArrayList<GenomeLoc>();
+
         for (GenomeLoc interval : intervals) {
-            if (interval.size() == 1)
-                bases.add(interval);
-            else {
-                for (int location = interval.getStart(); location <= interval.getStop(); location++) {
-                    bases.add(genomeLocParser.createGenomeLoc(interval.getContig(), location, location));
-                }
-            }
+            intervalStarts.add(interval.getStartLocation());
+            intervalStops.add(interval.getStopLocation());
         }
+
+        Map<GenomeLoc, ActiveRegion> baseRegionMap = new HashMap<GenomeLoc, ActiveRegion>();
+
+        for (ActiveRegion activeRegion : activeRegions) {
+            for (GenomeLoc activeLoc : toSingleBaseLocs(activeRegion.getLocation())) {
+                // Contract: Regions do not overlap
+                Assert.assertFalse(baseRegionMap.containsKey(activeLoc), "Genome location " + activeLoc + " is assigned to more than one region");
+                baseRegionMap.put(activeLoc, activeRegion);
+            }
+
+            GenomeLoc start = activeRegion.getLocation().getStartLocation();
+            if (intervalStarts.contains(start))
+                intervalStarts.remove(start);
+
+            GenomeLoc stop = activeRegion.getLocation().getStopLocation();
+            if (intervalStops.contains(stop))
+                intervalStops.remove(stop);
+        }
+
+        for (GenomeLoc baseLoc : toSingleBaseLocs(intervals)) {
+            // Contract: Each location in the interval(s) is in exactly one region
+            // Contract: The total set of regions exactly matches the analysis interval(s)
+            Assert.assertTrue(baseRegionMap.containsKey(baseLoc), "Genome location " + baseLoc + " is not assigned to any region");
+            baseRegionMap.remove(baseLoc);
+        }
+
+        // Contract: The total set of regions exactly matches the analysis interval(s)
+        Assert.assertEquals(baseRegionMap.size(), 0, "Active regions contain base(s) outside of the given intervals");
+
+        // Contract: All explicit interval boundaries must also be region boundaries
+        Assert.assertEquals(intervalStarts.size(), 0, "Interval start location does not match an active region start location");
+        Assert.assertEquals(intervalStops.size(), 0, "Interval stop location does not match an active region stop location");
+    }
+
+    private List<ActiveRegion> getActiveRegions(DummyActiveRegionWalker walker, List<GenomeLoc> intervals) {
+        for (LocusShardDataProvider dataProvider : createDataProviders(intervals))
+            t.traverse(walker, dataProvider, 0);
+
+        return walker.mappedActiveRegions;
+    }
+
+    private Collection<GenomeLoc> toSingleBaseLocs(GenomeLoc interval) {
+        List<GenomeLoc> bases = new ArrayList<GenomeLoc>();
+        if (interval.size() == 1)
+            bases.add(interval);
+        else {
+            for (int location = interval.getStart(); location <= interval.getStop(); location++)
+                bases.add(genomeLocParser.createGenomeLoc(interval.getContig(), location, location));
+        }
+
         return bases;
     }
 
-    private List<LocusShardDataProvider> createDataProviders(List<GenomeLoc> intervals) {
-        walker = new DummyActiveRegionWalker();
+    private Collection<GenomeLoc> toSingleBaseLocs(List<GenomeLoc> intervals) {
+        Set<GenomeLoc> bases = new TreeSet<GenomeLoc>();    // for sorting and uniqueness
+        for (GenomeLoc interval : intervals)
+            bases.addAll(toSingleBaseLocs(interval));
 
+        return bases;
+    }
+
+    private void verifyEqualIntervals(List<GenomeLoc> aIntervals, List<GenomeLoc> bIntervals) {
+        Collection<GenomeLoc> aBases = toSingleBaseLocs(aIntervals);
+        Collection<GenomeLoc> bBases = toSingleBaseLocs(bIntervals);
+
+        Assert.assertTrue(aBases.size() == bBases.size(), "Interval lists have a differing number of bases: " + aBases.size() + " vs. " + bBases.size());
+
+        Iterator<GenomeLoc> aIter = aBases.iterator();
+        Iterator<GenomeLoc> bIter = bBases.iterator();
+        while (aIter.hasNext() && bIter.hasNext()) {
+            GenomeLoc aLoc = aIter.next();
+            GenomeLoc bLoc = bIter.next();
+            Assert.assertTrue(aLoc.equals(bLoc), "Interval locations do not match: " + aLoc + " vs. " + bLoc);
+        }
+    }
+
+    private List<LocusShardDataProvider> createDataProviders(List<GenomeLoc> intervals) {
         GenomeAnalysisEngine engine = new GenomeAnalysisEngine();
         engine.setGenomeLocParser(genomeLocParser);
         t.initialize(engine);
@@ -146,8 +221,7 @@ public class TraverseActiveRegionsTest extends BaseTest {
         Shard shard = new MockLocusShard(genomeLocParser, intervals);
 
         List<LocusShardDataProvider> providers = new ArrayList<LocusShardDataProvider>();
-        WindowMaker windowMaker = new WindowMaker(shard,genomeLocParser,iterator,shard.getGenomeLocs());
-        for (WindowMaker.WindowMakerIterator window : windowMaker) {
+        for (WindowMaker.WindowMakerIterator window : new WindowMaker(shard, genomeLocParser, iterator, shard.getGenomeLocs())) {
             providers.add(new LocusShardDataProvider(shard, null, genomeLocParser, window.getLocus(), window, reference, new ArrayList<ReferenceOrderedDataSource>()));
         }