--- jsr166/src/test/tck/JSR166TestCase.java	2016/11/03 20:41:32	1.207
+++ jsr166/src/test/tck/JSR166TestCase.java	2016/11/05 16:09:50	1.208
@@ -41,6 +41,7 @@ import java.security.ProtectionDomain;
 import java.security.SecurityPermission;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
 import java.util.Enumeration;
@@ -1827,12 +1828,22 @@ public class JSR166TestCase extends Test
         }
     }
 
+    void assertImmutable(Object o) {
+        if (o instanceof Collection) {
+            assertThrows(
+                UnsupportedOperationException.class,
+                new Runnable() { public void run() {
+                        ((Collection) o).add(null);}});
+        }
+    }
+    
     @SuppressWarnings("unchecked")
     <T> T serialClone(T o) {
         try {
             ObjectInputStream ois = new ObjectInputStream
                 (new ByteArrayInputStream(serialBytes(o)));
             T clone = (T) ois.readObject();
+            if (o == clone) assertImmutable(o);
             assertSame(o.getClass(), clone.getClass());
             return clone;
         } catch (Throwable fail) {
@@ -1841,6 +1852,26 @@ public class JSR166TestCase extends Test
         }
     }
 
+    /**
+     * If o implements Cloneable and has a public clone method,
+     * returns a clone of o, else null.
+     */
+    @SuppressWarnings("unchecked")
+    <T> T cloneableClone(T o) {
+        if (!(o instanceof Cloneable)) return null;
+        final T clone;
+        try {
+            clone = (T) o.getClass().getMethod("clone").invoke(o);
+        } catch (NoSuchMethodException ok) {
+            return null;
+        } catch (ReflectiveOperationException unexpected) {
+            throw new Error(unexpected);
+        }
+        assertNotSame(o, clone); // not 100% guaranteed by spec
+        assertSame(o.getClass(), clone.getClass());
+        return clone;
+    }
+
     public void assertThrows(Class<? extends Throwable> expectedExceptionClass,
                              Runnable... throwingActions) {
         for (Runnable throwingAction : throwingActions) {