--- /dev/null	2019-11-19 22:05:02.069813242 -0800
+++ new/test/hotspot/jtreg/runtime/cds/appcds/jigsaw/RedefineClassesInModuleGraphTransformer.java	2020-08-31 08:10:44.258813976 -0700
@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+import java.lang.instrument.ClassFileTransformer;
+import java.lang.instrument.IllegalClassFormatException;
+import java.security.ProtectionDomain;
+
+public class RedefineClassesInModuleGraphTransformer implements ClassFileTransformer {
+    public byte[] transform(ClassLoader loader, String name, Class<?> classBeingRedefined,
+                            ProtectionDomain pd, byte[] buffer) throws IllegalClassFormatException {
+        System.out.println("transforming " + name);
+
+        if (name.equals("java/lang/Module")  || 
+            name.equals("java/lang/ModuleLayer")  || 
+            name.equals("java/lang/module/ResolvedModule")) {
+            throw new RuntimeException("Classes used by the module graph should never be transformed by Java agent");
+        }
+        return null;
+    }
+}