--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.jvmci.debug.test/src/com/oracle/jvmci/debug/test/DebugTimerTest.java	Tue May 26 23:21:15 2015 +0200
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2013, 2013, 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.jvmci.debug.test;
+
+import static org.junit.Assert.*;
+
+import java.lang.management.*;
+
+import org.junit.*;
+
+import com.oracle.jvmci.debug.*;
+
+
+public class DebugTimerTest {
+
+    private static final ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();
+
+    /**
+     * Actively spins the current thread for at least a given number of milliseconds in such a way
+     * that timers for the current thread keep ticking over.
+     *
+     * @return the number of milliseconds actually spent spinning which is guaranteed to be >=
+     *         {@code ms}
+     */
+    private static long spin(long ms) {
+        long start = threadMXBean.getCurrentThreadCpuTime();
+        do {
+            long durationMS = (threadMXBean.getCurrentThreadCpuTime() - start) / 1000;
+            if (durationMS >= ms) {
+                return durationMS;
+            }
+        } while (true);
+    }
+
+    @Test
+    public void test1() {
+        DebugConfig debugConfig = Debug.fixedConfig(0, 0, false, false, true, false, null, null, System.out);
+        try (DebugConfigScope dcs = new DebugConfigScope(debugConfig); Debug.Scope s = Debug.scope("DebugTimerTest")) {
+
+            DebugTimer timerA = Debug.timer("TimerA");
+            DebugTimer timerB = Debug.timer("TimerB");
+
+            long spinA;
+            long spinB;
+
+            try (DebugCloseable a1 = timerA.start()) {
+                spinA = spin(50);
+                try (DebugCloseable b1 = timerB.start()) {
+                    spinB = spin(50);
+                }
+            }
+
+            Assert.assertTrue(timerB.getCurrentValue() < timerA.getCurrentValue());
+            if (timerA.getFlat() != null && timerB.getFlat() != null) {
+                assertTrue(spinB >= spinA || timerB.getFlat().getCurrentValue() < timerA.getFlat().getCurrentValue());
+                assertEquals(timerA.getFlat().getCurrentValue(), timerA.getCurrentValue() - timerB.getFlat().getCurrentValue(), 10D);
+            }
+        }
+    }
+
+    @Test
+    public void test2() {
+        DebugConfig debugConfig = Debug.fixedConfig(0, 0, false, false, true, false, null, null, System.out);
+        try (DebugConfigScope dcs = new DebugConfigScope(debugConfig); Debug.Scope s = Debug.scope("DebugTimerTest")) {
+            DebugTimer timerC = Debug.timer("TimerC");
+            try (DebugCloseable c1 = timerC.start()) {
+                spin(50);
+                try (DebugCloseable c2 = timerC.start()) {
+                    spin(50);
+                    try (DebugCloseable c3 = timerC.start()) {
+                        spin(50);
+                        try (DebugCloseable c4 = timerC.start()) {
+                            spin(50);
+                            try (DebugCloseable c5 = timerC.start()) {
+                                spin(50);
+                            }
+                        }
+                    }
+                }
+            }
+            if (timerC.getFlat() != null) {
+                assertEquals(timerC.getFlat().getCurrentValue(), timerC.getCurrentValue());
+            }
+        }
+    }
+
+    @Test
+    public void test3() {
+        DebugConfig debugConfig = Debug.fixedConfig(0, 0, false, false, true, false, null, null, System.out);
+        try (DebugConfigScope dcs = new DebugConfigScope(debugConfig); Debug.Scope s = Debug.scope("DebugTimerTest")) {
+
+            DebugTimer timerD = Debug.timer("TimerD");
+            DebugTimer timerE = Debug.timer("TimerE");
+
+            long spinD1;
+            long spinE;
+
+            try (DebugCloseable d1 = timerD.start()) {
+                spinD1 = spin(50);
+                try (DebugCloseable e1 = timerE.start()) {
+                    spinE = spin(50);
+                    try (DebugCloseable d2 = timerD.start()) {
+                        spin(50);
+                        try (DebugCloseable d3 = timerD.start()) {
+                            spin(50);
+                        }
+                    }
+                }
+            }
+
+            Assert.assertTrue(timerE.getCurrentValue() < timerD.getCurrentValue());
+            if (timerD.getFlat() != null && timerE.getFlat() != null) {
+                assertTrue(spinE >= spinD1 || timerE.getFlat().getCurrentValue() < timerD.getFlat().getCurrentValue());
+                assertEquals(timerD.getFlat().getCurrentValue(), timerD.getCurrentValue() - timerE.getFlat().getCurrentValue(), 10D);
+            }
+        }
+    }
+}