Index: lucene/common-build.xml
===================================================================
--- lucene/common-build.xml	(revision 988752)
+++ lucene/common-build.xml	(working copy)
@@ -66,7 +66,7 @@
   <property name="tests.codec" value="random" />
   <property name="tests.locale" value="random" />
   <property name="tests.timezone" value="random" />
-  <property name="tests.directory" value="RAMDirectory" />
+  <property name="tests.directory" value="random" />
     
   <property name="javac.deprecation" value="off"/>
   <property name="javac.debug" value="on"/>
Index: lucene/src/test/org/apache/lucene/index/TestTermVectorsReader.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestTermVectorsReader.java	(revision 988752)
+++ lucene/src/test/org/apache/lucene/index/TestTermVectorsReader.java	(working copy)
@@ -394,6 +394,8 @@
       fail();
     } catch (IOException e) {
       // expected exception
+    } catch (IllegalArgumentException e) {
+      // mmapdir will give us this from java.nio.Buffer.position()
     } finally {
       reader.close();
     }
@@ -404,6 +406,8 @@
       fail();
     } catch (IOException e) {
       // expected exception
+    } catch (IllegalArgumentException e) {
+      // mmapdir will give us this from java.nio.Buffer.position()
     } finally {
       reader.close();
     }
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 {
Index: lucene/src/test/org/apache/lucene/index/TestTransactionRollback.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestTransactionRollback.java	(revision 988752)
+++ lucene/src/test/org/apache/lucene/index/TestTransactionRollback.java	(working copy)
@@ -126,8 +126,8 @@
   @Override
   protected void setUp() throws Exception {
     super.setUp();
+    random = newRandom();
     dir = newDirectory(random);
-		random = newRandom();
     //Build index, of records 1 to 100, committing after each batch of 10
     IndexDeletionPolicy sdp=new KeepAllDeletionPolicy();
     IndexWriter w=new IndexWriter(dir, newIndexWriterConfig(random, TEST_VERSION_CURRENT, new MockAnalyzer()).setIndexDeletionPolicy(sdp));
Index: lucene/src/test/org/apache/lucene/util/LuceneTestCaseJ4.java
===================================================================
--- lucene/src/test/org/apache/lucene/util/LuceneTestCaseJ4.java	(revision 988752)
+++ lucene/src/test/org/apache/lucene/util/LuceneTestCaseJ4.java	(working copy)
@@ -27,6 +27,7 @@
 import org.apache.lucene.search.FieldCache;
 import org.apache.lucene.search.FieldCache.CacheEntry;
 import org.apache.lucene.store.Directory;
+import org.apache.lucene.store.MMapDirectory;
 import org.apache.lucene.store.MockDirectoryWrapper;
 import org.apache.lucene.store.RAMDirectory;
 import org.apache.lucene.util.FieldCacheSanityChecker.Insanity;
@@ -72,6 +73,7 @@
 import java.util.regex.Pattern;
 import java.util.regex.Matcher;
 import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
 import static org.junit.Assert.assertEquals;
@@ -152,7 +154,7 @@
   /** Gets the timezone to run tests with */
   static final String TEST_TIMEZONE = System.getProperty("tests.timezone", "random");
   /** Gets the directory to run tests with */
-  static final String TEST_DIRECTORY = System.getProperty("tests.directory", "RAMDirectory");
+  static final String TEST_DIRECTORY = System.getProperty("tests.directory", "random");
   
   private static final Pattern codecWithParam = Pattern.compile("(.*)\\(\\s*(\\d+)\\s*\\)");
 
@@ -588,7 +590,7 @@
 
   public static MockDirectoryWrapper newDirectory(Random r) throws IOException {
     StackTraceElement[] stack = new Exception().getStackTrace();
-    Directory impl = newDirectoryImpl(TEST_DIRECTORY);
+    Directory impl = newDirectoryImpl(r, TEST_DIRECTORY);
     MockDirectoryWrapper dir = new MockDirectoryWrapper(impl);
     stores.put(dir, stack);
     return dir;
@@ -596,7 +598,7 @@
   
   public static MockDirectoryWrapper newDirectory(Random r, Directory d) throws IOException {
     StackTraceElement[] stack = new Exception().getStackTrace();
-    Directory impl = newDirectoryImpl(TEST_DIRECTORY);
+    Directory impl = newDirectoryImpl(r, TEST_DIRECTORY);
     for (String file : d.listAll()) {
      d.copy(impl, file, file);
     }
@@ -628,7 +630,24 @@
     }
   }
 
-  static Directory newDirectoryImpl(String clazzName) {
+  private static String CORE_DIRECTORIES[] = {
+    "RAMDirectory",
+    "SimpleFSDirectory",
+    "NIOFSDirectory",
+    "MMapDirectory"
+  };
+  
+  public static String randomDirectory(Random random) {
+    if (random.nextInt(10) == 0) {
+      return CORE_DIRECTORIES[random.nextInt(CORE_DIRECTORIES.length)];
+    } else {
+      return "RAMDirectory";
+    }
+  }
+  
+  static Directory newDirectoryImpl(Random random, String clazzName) {
+    if (clazzName.equals("random"))
+      clazzName = randomDirectory(random);
     if (clazzName.indexOf(".") == -1) // if not fully qualified, assume .store
       clazzName = "org.apache.lucene.store." + clazzName;
     try {
@@ -642,7 +661,11 @@
         tmpFile.mkdir();
         try {
           Constructor<? extends Directory> ctor = clazz.getConstructor(File.class);
-          return ctor.newInstance(tmpFile);
+          Directory d = ctor.newInstance(tmpFile);
+          // try not to enable this hack unless we must.
+          if (d instanceof MMapDirectory && Constants.WINDOWS && MMapDirectory.UNMAP_SUPPORTED)
+            ((MMapDirectory)d).setUseUnmap(true);
+          return d;
         } catch (Exception e2) {
           // try .open(File)
           Method method = clazz.getMethod("open", new Class[] { File.class });
Index: lucene/src/test/org/apache/lucene/util/LuceneTestCase.java
===================================================================
--- lucene/src/test/org/apache/lucene/util/LuceneTestCase.java	(revision 988752)
+++ lucene/src/test/org/apache/lucene/util/LuceneTestCase.java	(working copy)
@@ -335,7 +335,7 @@
 
   public MockDirectoryWrapper newDirectory(Random r) throws IOException {
     StackTraceElement[] stack = new Exception().getStackTrace();
-    Directory impl = LuceneTestCaseJ4.newDirectoryImpl(TEST_DIRECTORY);
+    Directory impl = LuceneTestCaseJ4.newDirectoryImpl(r, TEST_DIRECTORY);
     MockDirectoryWrapper dir = new MockDirectoryWrapper(impl);
     stores.put(dir, stack);
     return dir;
@@ -343,7 +343,7 @@
   
   public MockDirectoryWrapper newDirectory(Random r, Directory d) throws IOException {
     StackTraceElement[] stack = new Exception().getStackTrace();
-    Directory impl = LuceneTestCaseJ4.newDirectoryImpl(TEST_DIRECTORY);
+    Directory impl = LuceneTestCaseJ4.newDirectoryImpl(r, TEST_DIRECTORY);
     for (String file : d.listAll()) {
      d.copy(impl, file, file);
     }