Index: lucene/src/test/org/apache/lucene/index/TestIndexReader.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestIndexReader.java	(revision 1026400)
+++ lucene/src/test/org/apache/lucene/index/TestIndexReader.java	(working copy)
@@ -970,6 +970,9 @@
             }
           }
 
+          // turn off random IOExceptions for the verification step
+          dir.setRandomIOExceptionRate(0.0D);
+          
           // Whether we succeeded or failed, check that all
           // un-referenced files were in fact deleted (ie,
           // we did not create garbage).  Just create a
Index: lucene/src/test/org/apache/lucene/index/TestTransactions.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestTransactions.java	(revision 1026400)
+++ lucene/src/test/org/apache/lucene/index/TestTransactions.java	(working copy)
@@ -168,10 +168,18 @@
 
     @Override
     public void doWork() throws Throwable {
-      IndexReader r1, r2;
+      IndexReader r1 = null, r2 = null;
       synchronized(lock) {
-        r1 = IndexReader.open(dir1, true);
-        r2 = IndexReader.open(dir2, true);
+        try {
+          r1 = IndexReader.open(dir1, true);
+          r2 = IndexReader.open(dir2, true);
+        } catch (IOException e) {
+          if (!e.getMessage().contains("on purpose"))
+            throw e;
+          if (r1 != null) r1.close();
+          if (r2 != null) r2.close();
+          return;
+        }
       }
       if (r1.numDocs() != r2.numDocs())
         throw new RuntimeException("doc counts differ: r1=" + r1.numDocs() + " r2=" + r2.numDocs());
Index: lucene/src/test/org/apache/lucene/index/TestIndexWriterDelete.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestIndexWriterDelete.java	(revision 1026400)
+++ lucene/src/test/org/apache/lucene/index/TestIndexWriterDelete.java	(working copy)
@@ -539,6 +539,9 @@
           TestIndexWriter.assertNoUnreferencedFiles(dir, "after writer.close");
         }
 
+        // turn off random IOExceptions for the verification step
+        dir.setRandomIOExceptionRate(0.0D); 
+        
         // Finally, verify index is not corrupt, and, if
         // we succeeded, we see all docs changed, and if
         // we failed, we see either all docs or no docs
Index: lucene/src/test/org/apache/lucene/store/MockDirectoryWrapper.java
===================================================================
--- lucene/src/test/org/apache/lucene/store/MockDirectoryWrapper.java	(revision 1026400)
+++ lucene/src/test/org/apache/lucene/store/MockDirectoryWrapper.java	(working copy)
@@ -209,6 +209,15 @@
     // seed so we have deterministic behaviour:
     randomState = new Random(seed);
   }
+  
+  /** 
+   * Do not use. Use setRandomIOExceptionRate(double, long). 
+   * @lucene.internal
+   */
+  public void setRandomIOExceptionRate(double rate) {
+    randomIOExceptionRate = rate;
+  }
+  
   public double getRandomIOExceptionRate() {
     return randomIOExceptionRate;
   }
@@ -217,7 +226,7 @@
     if (randomIOExceptionRate > 0.0) {
       int number = Math.abs(randomState.nextInt() % 1000);
       if (number < randomIOExceptionRate*1000) {
-        throw new IOException("a random IOException");
+        throw new FakeIOException("a random IOException");
       }
     }
   }
@@ -246,6 +255,7 @@
 
   @Override
   public synchronized IndexOutput createOutput(String name) throws IOException {
+    maybeThrowAnyException();
     if (crashed)
       throw new IOException("cannot createOutput after crash");
     init();
@@ -284,6 +294,7 @@
 
   @Override
   public synchronized IndexInput openInput(String name) throws IOException {
+    maybeThrowAnyException();
     if (!delegate.fileExists(name))
       throw new FileNotFoundException(name);
     else {
@@ -414,6 +425,16 @@
       }
     }
   }
+  
+  /**
+   * might throw a deterministic exception, if any have been registered
+   * with failOn, and might throw an IOException, if random IO Exceptions
+   * are turned on with setRandomIOExceptionRate.
+   */
+  synchronized void maybeThrowAnyException() throws IOException {
+    maybeThrowDeterministicException();
+    maybeThrowIOException();
+  }
 
   @Override
   public synchronized String[] listAll() throws IOException {
@@ -469,4 +490,10 @@
   public synchronized void copy(Directory to, String src, String dest) throws IOException {
     delegate.copy(to, src, dest);
   }
+  
+  public static class FakeIOException extends IOException {
+    public FakeIOException(String message) {
+      super(message);
+    }
+  }
 }
Index: lucene/src/test/org/apache/lucene/util/_TestUtil.java
===================================================================
--- lucene/src/test/org/apache/lucene/util/_TestUtil.java	(revision 1026400)
+++ lucene/src/test/org/apache/lucene/util/_TestUtil.java	(working copy)
@@ -27,6 +27,8 @@
 import org.apache.lucene.index.codecs.Codec;
 import org.apache.lucene.index.SegmentWriteState;
 import org.apache.lucene.store.Directory;
+import org.apache.lucene.store.MockDirectoryWrapper;
+
 import java.io.ByteArrayOutputStream;
 import java.io.PrintStream;
 import java.util.Random;
@@ -69,11 +71,24 @@
    *  issues are hit, a RuntimeException is thrown; else,
    *  true is returned. */
   public static CheckIndex.Status checkIndex(Directory dir) throws IOException {
+    // hack alert: turn off random IOExceptions temporarily
+    double randomExceptionRateSave = 0.0D;
+    if (dir instanceof MockDirectoryWrapper) {
+      MockDirectoryWrapper m = (MockDirectoryWrapper) dir;
+      randomExceptionRateSave = m.getRandomIOExceptionRate();
+      m.setRandomIOExceptionRate(0.0D);
+    }
+    
     ByteArrayOutputStream bos = new ByteArrayOutputStream(1024);
 
     CheckIndex checker = new CheckIndex(dir);
     checker.setInfoStream(new PrintStream(bos));
     CheckIndex.Status indexStatus = checker.checkIndex();
+    
+    // restore the random IOException rate
+    if (randomExceptionRateSave > 0.0D)
+      ((MockDirectoryWrapper)dir).setRandomIOExceptionRate(randomExceptionRateSave);
+    
     if (indexStatus == null || indexStatus.clean == false) {
       System.out.println("CheckIndex failed");
       System.out.println(bos.toString());