Index: lucene/src/test/org/apache/lucene/index/TestIndexWriter.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestIndexWriter.java	(revision 988752)
+++ lucene/src/test/org/apache/lucene/index/TestIndexWriter.java	(working copy)
@@ -4377,10 +4377,8 @@
 
     @Override
     public void run() {
-      Directory dir;
-      try { 
-        dir = newDirectory(random); 
-      } catch (IOException e) { throw new RuntimeException(e); }
+      // LUCENE-2239: won't work with NIOFS/MMAP
+      Directory dir = new MockDirectoryWrapper(new RAMDirectory()); 
       IndexWriter w = null;
       while(!finish) {
         try {