diff --git a/mozilla/xpcom/tests/utils/WhatError.cpp b/mozilla/xpcom/tests/utils/WhatError.cpp
new file mode 100644
index 00000000000..0480b2b239a
--- /dev/null
+++ b/mozilla/xpcom/tests/utils/WhatError.cpp
@@ -0,0 +1,46 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ *
+ * The contents of this file are subject to the Netscape Public
+ * License Version 1.1 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of
+ * the License at http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS
+ * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * rights and limitations under the License.
+ *
+ * The Original Code is mozilla.org code.
+ *
+ * The Initial Developer of the Original Code is Netscape
+ * Communications Corporation.  Portions created by Netscape are
+ * Copyright (C) 1998 Netscape Communications Corporation. All
+ * Rights Reserved.
+ *
+ * Contributor(s): 
+ */
+
+#include "nsError.h"
+#include <stdlib.h>
+#include <stdio.h>
+
+int
+main(int argc, char **argv)
+{
+    int errorCode = 0;
+    char buffer[100];
+    
+    if (argc != 2)
+        return -1;
+
+    sscanf( argv[1], "0x%x", &errorCode);
+    sprintf(buffer, "%d", errorCode);
+    sscanf( buffer, "%d", &errorCode);
+    
+    printf( "Code: %d, Module: %d, Severity: %d\n", 
+            NS_ERROR_GET_CODE(errorCode), 
+            NS_ERROR_GET_MODULE(errorCode), 
+            NS_ERROR_GET_SEVERITY(errorCode));
+
+    return 0;
+}