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diff --git a/jsr166-tests/src/test/java/jsr166/SystemTest.java b/jsr166-tests/src/test/java/jsr166/SystemTest.java
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+++ b/jsr166-tests/src/test/java/jsr166/SystemTest.java
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+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ * Other contributors include Andrew Wright, Jeffrey Hayes,
+ * Pat Fisher, Mike Judd.
+ */
+
+package jsr166;
+
+import junit.framework.*;
+
+public class SystemTest extends JSR166TestCase {
+
+    /**
+     * Worst case rounding for millisecs; set for 60 cycle millis clock.
+     * This value might need to be changed on JVMs with coarser
+     * System.currentTimeMillis clocks.
+     */
+    static final long MILLIS_ROUND = 17;
+
+    /**
+     * Nanos between readings of millis is no longer than millis (plus
+     * possible rounding).
+     * This shows only that nano timing not (much) worse than milli.
+     */
+    public void testNanoTime1() throws InterruptedException {
+        long m1 = System.currentTimeMillis();
+        Thread.sleep(1);
+        long n1 = System.nanoTime();
+        Thread.sleep(SHORT_DELAY_MS);
+        long n2 = System.nanoTime();
+        Thread.sleep(1);
+        long m2 = System.currentTimeMillis();
+        long millis = m2 - m1;
+        long nanos = n2 - n1;
+        assertTrue(nanos >= 0);
+        long nanosAsMillis = nanos / 1000000;
+        assertTrue(nanosAsMillis <= millis + MILLIS_ROUND);
+    }
+
+    /**
+     * Millis between readings of nanos is less than nanos, adjusting
+     * for rounding.
+     * This shows only that nano timing not (much) worse than milli.
+     */
+    public void testNanoTime2() throws InterruptedException {
+        long n1 = System.nanoTime();
+        Thread.sleep(1);
+        long m1 = System.currentTimeMillis();
+        Thread.sleep(SHORT_DELAY_MS);
+        long m2 = System.currentTimeMillis();
+        Thread.sleep(1);
+        long n2 = System.nanoTime();
+        long millis = m2 - m1;
+        long nanos = n2 - n1;
+
+        assertTrue(nanos >= 0);
+        long nanosAsMillis = nanos / 1000000;
+        assertTrue(millis <= nanosAsMillis + MILLIS_ROUND);
+    }
+
+}