Index: src/test/org/apache/lucene/search/MockFilter.java
===================================================================
--- src/test/org/apache/lucene/search/MockFilter.java	(revision 611258)
+++ src/test/org/apache/lucene/search/MockFilter.java	(working copy)
@@ -18,14 +18,15 @@
  */
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.util.DocIdBitSet;
 import java.util.BitSet;
 
 public class MockFilter extends Filter {
   private boolean wasCalled;
 
-  public BitSet bits(IndexReader reader) {
+  public DocIdSet getDocIdSet(IndexReader reader) {
     wasCalled = true;
-    return new BitSet();
+    return new DocIdBitSet(new BitSet());
   }
 
   public void clear() {
Index: src/test/org/apache/lucene/search/SingleDocTestFilter.java
===================================================================
--- src/test/org/apache/lucene/search/SingleDocTestFilter.java	(revision 611258)
+++ src/test/org/apache/lucene/search/SingleDocTestFilter.java	(working copy)
@@ -18,6 +18,7 @@
  */
 
 import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.util.DocIdBitSet;
 
 import java.util.BitSet;
 import java.io.IOException;
@@ -29,9 +30,9 @@
     this.doc = doc;
   }
 
-  public BitSet bits(IndexReader reader) throws IOException {
+  public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
     BitSet bits = new BitSet(reader.maxDoc());
     bits.set(doc);
-    return bits;
+    return new DocIdBitSet(bits);
   }
 }
Index: src/test/org/apache/lucene/search/TestExplanations.java
===================================================================
--- src/test/org/apache/lucene/search/TestExplanations.java	(revision 611258)
+++ src/test/org/apache/lucene/search/TestExplanations.java	(working copy)
@@ -33,6 +33,7 @@
 import org.apache.lucene.queryParser.ParseException;
 
 import org.apache.lucene.util.LuceneTestCase;
+import org.apache.lucene.util.DocIdBitSet;
 
 import java.util.Random;
 import java.util.BitSet;
@@ -121,12 +122,12 @@
     public ItemizedFilter(int[] docs) {
       this.docs = docs;
     }
-    public BitSet bits(IndexReader r) {
+    public DocIdSet getDocIdSet(IndexReader r) {
       BitSet b = new BitSet(r.maxDoc());
       for (int i = 0; i < docs.length; i++) {
         b.set(docs[i]);
       }
-      return b;
+      return new DocIdBitSet(b);
     }
   }
 
Index: src/test/org/apache/lucene/search/TestFilteredQuery.java
===================================================================
--- src/test/org/apache/lucene/search/TestFilteredQuery.java	(revision 611258)
+++ src/test/org/apache/lucene/search/TestFilteredQuery.java	(working copy)
@@ -26,6 +26,7 @@
 import org.apache.lucene.search.BooleanClause.Occur;
 import org.apache.lucene.store.RAMDirectory;
 import org.apache.lucene.util.LuceneTestCase;
+import org.apache.lucene.util.DocIdBitSet;
 
 import java.util.BitSet;
 
@@ -82,11 +83,11 @@
   // must be static for serialization tests
   private static Filter newStaticFilterB() {
     return new Filter() {
-      public BitSet bits (IndexReader reader) {
+      public DocIdSet getDocIdSet (IndexReader reader) {
         BitSet bitset = new BitSet(5);
         bitset.set (1);
         bitset.set (3);
-        return bitset;
+        return new DocIdBitSet(bitset);
       }
     };
   }
@@ -150,10 +151,10 @@
   // must be static for serialization tests 
   private static Filter newStaticFilterA() {
     return new Filter() {
-      public BitSet bits (IndexReader reader) {
+      public DocIdSet getDocIdSet (IndexReader reader) {
         BitSet bitset = new BitSet(5);
         bitset.set(0, 5);
-        return bitset;
+        return new DocIdBitSet(bitset);
       }
     };
   }
Index: src/test/org/apache/lucene/search/TestScorerPerf.java
===================================================================
--- src/test/org/apache/lucene/search/TestScorerPerf.java	(revision 611258)
+++ src/test/org/apache/lucene/search/TestScorerPerf.java	(working copy)
@@ -95,16 +95,6 @@
     return sets;
   }
 
-  public static class BitSetFilter extends Filter {
-    public BitSet set;
-    public BitSetFilter(BitSet set) {
-      this.set = set;
-    }
-    public BitSet bits(IndexReader reader) throws IOException {
-      return set;
-    }
-  }
-
   public static class CountingHitCollector extends HitCollector {
     int count=0;
     int sum=0;
@@ -137,8 +127,12 @@
 
 
   BitSet addClause(BooleanQuery bq, BitSet result) {
-    BitSet rnd = sets[r.nextInt(sets.length)];
-    Query q = new ConstantScoreQuery(new BitSetFilter(rnd));
+    final BitSet rnd = sets[r.nextInt(sets.length)];
+    Query q = new ConstantScoreQuery(new BitSetFilter() {
+      public BitSet bits(IndexReader reader) {
+        return rnd;
+      };
+    });
     bq.add(q, BooleanClause.Occur.MUST);
     if (validate) {
       if (result==null) result = (BitSet)rnd.clone();
Index: src/test/org/apache/lucene/search/TestSort.java
===================================================================
--- src/test/org/apache/lucene/search/TestSort.java	(revision 611258)
+++ src/test/org/apache/lucene/search/TestSort.java	(working copy)
@@ -28,6 +28,7 @@
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.store.RAMDirectory;
+import org.apache.lucene.util.DocIdBitSet;
 
 import java.io.IOException;
 import java.io.Serializable;
@@ -561,10 +562,10 @@
 
     // a filter that only allows through the first hit
     Filter filt = new Filter() {
-      public BitSet bits(IndexReader reader) throws IOException {
+      public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
         BitSet bs = new BitSet(reader.maxDoc());
         bs.set(docs1.scoreDocs[0].doc);
-        return bs;
+        return new DocIdBitSet(bs);
       }
     };