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diff --git a/jstests/use_power_of_2.js b/jstests/use_power_of_2.js
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+/* This test ensures that the usePowerOf2 user flag
+ * effectively reuses space. The test repeatedly inserts and
+ * then deletes a batch of variable-length strings, then checks
+ * that doing so does not cause the storageSize to grow. */
+
+// A bunch of strings of length 0 to 100
+var var_length_strings =
+    [ "" ,
+      "aaaaa" ,
+      "aaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ,
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ]
+
+//insert all the strings
+var batch_insert = function(coll){
+    for ( i=0; i < var_length_strings.length; i++ ){
+        coll.insert( { a : var_length_strings[i] } );
+    }
+}
+
+//delete the same strings
+var batch_delete = function(coll){
+    for ( i=0; i < var_length_strings.length; i++ ){
+        coll.remove( { a : var_length_strings[i] } );
+    }
+}
+
+//number of times to repeat batch inserts/deletes
+var numrepeats = 1000;
+
+var testStorageSize = function(ns){
+    //insert docs and measure storage size
+    batch_insert(ns);
+    var oldSize = ns.stats().storageSize;
+
+    //remove and add same docs a bunch of times
+    for ( n=0 ; n < numrepeats ; n++ ){
+        batch_delete(ns);
+        batch_insert(ns);
+    }
+
+    //check size didn't change
+    var newSize = ns.stats().storageSize;
+    assert.eq( oldSize , newSize , "storage size changed");
+}
+
+/****************** TEST 1 *****************************/
+
+//create fresh collection, set flag to true, test storage size
+var coll = "usepower1"
+var t = db.getCollection(coll);
+t.drop();
+db.createCollection(coll);
+var res = db.runCommand( { "collMod" : coll ,  "usePowerOf2Sizes" : true } );
+assert.eq( res.ok , 1 , "collMod failed" );
+
+res = db.runCommand( { "collMod" : coll , "usePowerOf2Sizess" : true } )
+assert.eq( res.ok , 0 , "collMod should have failed: " + tojson( res ) )
+
+testStorageSize(t);
+
+/**************** Test 2 *****************************/
+
+//repeat previous test, but with flag set at creation time
+var coll = "usepower2"
+var t = db.getCollection(coll);
+t.drop();
+db.runCommand({"create" : coll,  "flags" : 1 });
+
+testStorageSize(t);