--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/SafeReplaceTest.java	Tue Jan 27 20:24:54 2015 -0800
@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2015, 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.
+ */
+package com.oracle.truffle.api.test.nodes;
+
+import static org.junit.Assert.*;
+
+import org.junit.*;
+
+import com.oracle.truffle.api.frame.*;
+import com.oracle.truffle.api.nodes.*;
+
+/**
+ * Tests optional method for ensuring that a node replacement is type safe. Ordinary node
+ * replacement is performed by unsafe assignment of a parent node's child field.
+ */
+public class SafeReplaceTest {
+
+    @Test
+    public void testCorrectReplacement() {
+        TestRootNode root = new TestRootNode();
+        final TestNode oldChild = new TestNode();
+        root.child = oldChild;
+        assertFalse(oldChild.isReplaceable());  // No parent node
+        root.adoptChildren();
+        assertTrue(oldChild.isReplaceable());   // Now adopted by parent
+        final TestNode newChild = new TestNode();
+        assertTrue(oldChild.isSafelyReplaceableBy(newChild));  // Parent field type is assignable by
+        // new node
+        oldChild.replace(newChild);
+        root.execute(null);
+        assertEquals(root.executed, 1);
+        assertEquals(oldChild.executed, 0);
+        assertEquals(newChild.executed, 1);
+    }
+
+    @Test
+    public void testIncorrectReplacement() {
+        TestRootNode root = new TestRootNode();
+        final TestNode oldChild = new TestNode();
+        root.child = oldChild;
+        root.adoptChildren();
+        final WrongTestNode newChild = new WrongTestNode();
+        assertFalse(oldChild.isSafelyReplaceableBy(newChild));
+        // Can't test: oldChild.replace(newChild);
+        // Fails if assertions checked; else unsafe assignment will eventually crash the VM
+    }
+
+    private static class TestNode extends Node {
+
+        private int executed;
+
+        public Object execute() {
+            executed++;
+            return null;
+        }
+    }
+
+    private static class TestRootNode extends RootNode {
+
+        @Child TestNode child;
+
+        private int executed;
+
+        @Override
+        public Object execute(VirtualFrame frame) {
+            executed++;
+            child.execute();
+            return null;
+        }
+    }
+
+    private static class WrongTestNode extends Node {
+    }
+
+}