Add test for MonotonicClock

btm/src/test/java/bitronix/tm/utils/MonotonicClockTest.java

@@ -0,0 +1,57 @@
+package bitronix.tm.utils;
+
+import junit.framework.TestCase;
+
+/**
+ * Test for MonotonicClock
+ */
+public class MonotonicClockTest extends TestCase {
+
+	/**
+	 * MonotonicClock should increment always
+	 * (the increment may not be 1 always as granularity of system clock maybe > 1ms)
+	 */
+	public void testIncrement() {
+		long systemMillis = System.currentTimeMillis();
+		long lastCurrentTimeMillis = MonotonicClock.currentTimeMillis();
+		// Check on second
+		int i = 0;
+		int sameMilli=0;
+
+		// Test the increment for one second:
+		while (System.currentTimeMillis() < systemMillis + 1000) {
+			long currentTimeMillis = MonotonicClock.currentTimeMillis();
+			if (currentTimeMillis == lastCurrentTimeMillis) {
+				// same milli
+				sameMilli++;
+			} else {
+				assertTrue("Expected always growing increment but found (in iteration "+i+"): lastCurrentTimeMillis="+lastCurrentTimeMillis+ " > currentTimeMillis="+currentTimeMillis, 
+						lastCurrentTimeMillis < currentTimeMillis);
+			}
+			i++;
+		}
+		assertNotSame("Expected same millis in the loop above",0,sameMilli);
+	}
+
+	/**
+	 * bitronix.tm.resource.common.XAPool.shrink()
+	 * needs to know the seconds since last releaseTime,
+	 * so MonotonicClock needs to return values corresponding to "real" time when asking at different timestamps.
+	 * 
+	 * (Due to design the starting offset MonotonicClock.currentTimeMillis() and System.currentTimeMillis() varies)
+	 * 
+	 * @throws InterruptedException 
+	 */
+	public void testContinues() throws InterruptedException {
+
+		long lastCurrentTimeMillis = MonotonicClock.currentTimeMillis();
+
+		Thread.sleep(1000);
+
+		long now = MonotonicClock.currentTimeMillis();
+
+		long duration= now-lastCurrentTimeMillis;
+
+		assertTrue("Should be around one second (1000 ms) but was "+duration, 700<duration && duration< 1300);
+	}
+}