Index: lucene/src/test/org/apache/lucene/TestExternalCodecs.java
===================================================================
--- lucene/src/test/org/apache/lucene/TestExternalCodecs.java	(revision 1065716)
+++ lucene/src/test/org/apache/lucene/TestExternalCodecs.java	(working copy)
@@ -631,7 +631,8 @@
     
     
     final int NUM_DOCS = 173;
-    Directory dir = newDirectory();
+    MockDirectoryWrapper dir = newDirectory();
+    dir.setCheckIndexOnClose(false); // we use a custom codec provider
     IndexWriter w = new IndexWriter(
         dir,
         newIndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer(MockTokenizer.WHITESPACE, true, true)).
Index: lucene/src/test/org/apache/lucene/index/TestIndexWriterExceptions.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestIndexWriterExceptions.java	(revision 1065716)
+++ lucene/src/test/org/apache/lucene/index/TestIndexWriterExceptions.java	(working copy)
@@ -983,7 +983,8 @@
   // latest segments file and make sure we get an
   // IOException trying to open the index:
   public void testSimulatedCorruptIndex1() throws IOException {
-      Directory dir = newDirectory();
+      MockDirectoryWrapper dir = newDirectory();
+      dir.setCheckIndexOnClose(false); // we are corrupting it!
 
       IndexWriter writer = null;
 
@@ -1030,8 +1031,8 @@
   // files and make sure we get an IOException trying to
   // open the index:
   public void testSimulatedCorruptIndex2() throws IOException {
-      Directory dir = newDirectory();
-
+      MockDirectoryWrapper dir = newDirectory();
+      dir.setCheckIndexOnClose(false); // we are corrupting it!
       IndexWriter writer = null;
 
       writer  = new IndexWriter(
Index: lucene/src/test/org/apache/lucene/index/TestIndexWriterMerging.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestIndexWriterMerging.java	(revision 1065716)
+++ lucene/src/test/org/apache/lucene/index/TestIndexWriterMerging.java	(working copy)
@@ -66,7 +66,6 @@
     writer.close();
 
     fail = verifyIndex(merged, 0);
-    merged.close();
 
     assertFalse("The merged index is invalid", fail);
     indexA.close();
Index: lucene/src/test/org/apache/lucene/store/MockDirectoryWrapper.java
===================================================================
--- lucene/src/test/org/apache/lucene/store/MockDirectoryWrapper.java	(revision 1065716)
+++ lucene/src/test/org/apache/lucene/store/MockDirectoryWrapper.java	(working copy)
@@ -31,7 +31,9 @@
 import java.util.Random;
 import java.util.Set;
 
+import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.util.LuceneTestCase;
+import org.apache.lucene.util._TestUtil;
 
 /**
  * This is a Directory Wrapper that adds methods
@@ -48,6 +50,7 @@
   Random randomState;
   boolean noDeleteOpenFile = true;
   boolean preventDoubleWrite = true;
+  boolean checkIndexOnClose = true;
   boolean trackDiskUsage = false;
   private Set<String> unSyncedFiles;
   private Set<String> createdFiles;
@@ -206,6 +209,17 @@
   }
 
   /**
+   * Set whether or not checkindex should be run
+   * on close
+   */
+  public void setCheckIndexOnClose(boolean value) {
+    this.checkIndexOnClose = value;
+  }
+  
+  public boolean getCheckIndexOnClose() {
+    return checkIndexOnClose;
+  }
+  /**
    * If 0.0, no exceptions will be thrown.  Else this should
    * be a double 0.0 - 1.0.  We will randomly throw an
    * IOException on the first write to an OutputStream based
@@ -393,6 +407,9 @@
       throw new RuntimeException("MockDirectoryWrapper: cannot close: there are still open files: " + openFiles, cause);
     }
     open = false;
+    if (checkIndexOnClose && IndexReader.indexExists(this)) {
+      _TestUtil.checkIndex(this);
+    }
     delegate.close();
   }
 
Index: lucene/src/test/org/apache/lucene/store/TestFileSwitchDirectory.java
===================================================================
--- lucene/src/test/org/apache/lucene/store/TestFileSwitchDirectory.java	(revision 1065716)
+++ lucene/src/test/org/apache/lucene/store/TestFileSwitchDirectory.java	(working copy)
@@ -39,8 +39,10 @@
     fileExtensions.add(IndexFileNames.FIELDS_EXTENSION);
     fileExtensions.add(IndexFileNames.FIELDS_INDEX_EXTENSION);
     
-    Directory primaryDir = new MockDirectoryWrapper(random, new RAMDirectory());
-    Directory secondaryDir = new MockDirectoryWrapper(random, new RAMDirectory());
+    MockDirectoryWrapper primaryDir = new MockDirectoryWrapper(random, new RAMDirectory());
+    primaryDir.setCheckIndexOnClose(false); // only part of an index
+    MockDirectoryWrapper secondaryDir = new MockDirectoryWrapper(random, new RAMDirectory());
+    secondaryDir.setCheckIndexOnClose(false); // only part of an index
     
     FileSwitchDirectory fsd = new FileSwitchDirectory(fileExtensions, primaryDir, secondaryDir, true);
     IndexWriter writer = new IndexWriter(