Index: lucene/src/java/org/apache/lucene/index/codecs/standard/StandardPostingsWriter.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/codecs/standard/StandardPostingsWriter.java	(revision 1091277)
+++ lucene/src/java/org/apache/lucene/index/codecs/standard/StandardPostingsWriter.java	(working copy)
@@ -50,12 +50,13 @@
    * smaller indexes, greater acceleration, but fewer accelerable cases, while
    * smaller values result in bigger indexes, less acceleration and more
    * accelerable cases. More detailed experiments would be useful here. */
-  final int skipInterval = 16;
+  static final int DEFAULT_SKIP_INTERVAL = 16;
+  final int skipInterval;
   
   /**
    * Expert: minimum docFreq to write any skip data at all
    */
-  final int skipMinimum = skipInterval;
+  final int skipMinimum;
 
   /** Expert: The maximum number of skip levels. Smaller values result in 
    * slightly smaller indexes, but slower skipping in big posting lists.
@@ -82,7 +83,12 @@
   private RAMOutputStream bytesWriter = new RAMOutputStream();
 
   public StandardPostingsWriter(SegmentWriteState state) throws IOException {
+    this(state, DEFAULT_SKIP_INTERVAL);
+  }
+  public StandardPostingsWriter(SegmentWriteState state, int skipInterval) throws IOException {
     super();
+    this.skipInterval = skipInterval;
+    this.skipMinimum = skipInterval; /* set to the same for now */
     //this.segment = state.segmentName;
     String fileName = IndexFileNames.segmentFileName(state.segmentName, state.codecId, StandardCodec.FREQ_EXTENSION);
     freqOut = state.directory.createOutput(fileName);
Index: lucene/src/java/org/apache/lucene/index/codecs/sep/SepPostingsWriterImpl.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/codecs/sep/SepPostingsWriterImpl.java	(revision 1091277)
+++ lucene/src/java/org/apache/lucene/index/codecs/sep/SepPostingsWriterImpl.java	(working copy)
@@ -69,12 +69,13 @@
    * smaller indexes, greater acceleration, but fewer accelerable cases, while
    * smaller values result in bigger indexes, less acceleration and more
    * accelerable cases. More detailed experiments would be useful here. */
-  final int skipInterval = 16;
+  final int skipInterval;
+  static final int DEFAULT_SKIP_INTERVAL = 16;
   
   /**
    * Expert: minimum docFreq to write any skip data at all
    */
-  final int skipMinimum = skipInterval;
+  final int skipMinimum;
 
   /** Expert: The maximum number of skip levels. Smaller values result in 
    * slightly smaller indexes, but slower skipping in big posting lists.
@@ -102,8 +103,13 @@
   private final RAMOutputStream indexBytesWriter = new RAMOutputStream();
 
   public SepPostingsWriterImpl(SegmentWriteState state, IntStreamFactory factory) throws IOException {
+    this(state, factory, DEFAULT_SKIP_INTERVAL);
+  }
+
+  public SepPostingsWriterImpl(SegmentWriteState state, IntStreamFactory factory, int skipInterval) throws IOException {
     super();
-
+    this.skipInterval = skipInterval;
+    this.skipMinimum = skipInterval; /* set to the same for now */
     final String docFileName = IndexFileNames.segmentFileName(state.segmentName, state.codecId, DOC_EXTENSION);
     docOut = factory.createOutput(state.directory, docFileName);
     docIndex = docOut.index();
Index: lucene/src/test-framework/org/apache/lucene/index/codecs/mockrandom/MockRandomCodec.java
===================================================================
--- lucene/src/test-framework/org/apache/lucene/index/codecs/mockrandom/MockRandomCodec.java	(revision 1091277)
+++ lucene/src/test-framework/org/apache/lucene/index/codecs/mockrandom/MockRandomCodec.java	(working copy)
@@ -135,13 +135,20 @@
     final Random random = new Random(seed);
     PostingsWriterBase postingsWriter;
 
+    // TODO: intentionally made a new random here to not interfere with mockrandom's magical seeding!!!
+    // maybe this code should be moved to before it writes the seed at all?! 
+    int skipInterval = _TestUtil.nextInt(new Random(seed), 2, 64);
+    if (LuceneTestCase.VERBOSE) {
+      System.out.println("MockRandomCodec: skipInterval=" + skipInterval);
+    }
+
     if (random.nextBoolean()) {
-      postingsWriter = new SepPostingsWriterImpl(state, new MockIntStreamFactory(random));
+      postingsWriter = new SepPostingsWriterImpl(state, new MockIntStreamFactory(random), skipInterval);
     } else {
       if (LuceneTestCase.VERBOSE) {
         System.out.println("MockRandomCodec: writing Standard postings");
       }
-      postingsWriter = new StandardPostingsWriter(state);
+      postingsWriter = new StandardPostingsWriter(state, skipInterval);
     }
 
     if (random.nextBoolean()) {