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/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)
@@ -246,6 +246,7 @@
 
   @Override
   public synchronized IndexOutput createOutput(String name) throws IOException {
+    maybeThrowDeterministicException();
     if (crashed)
       throw new IOException("cannot createOutput after crash");
     init();
@@ -284,6 +285,7 @@
 
   @Override
   public synchronized IndexInput openInput(String name) throws IOException {
+    maybeThrowDeterministicException();
     if (!delegate.fileExists(name))
       throw new FileNotFoundException(name);
     else {