The test fails because the testSleep test fails to meet the 4000msec upper bound constraint of the sleep timeout. This upper bound seems unnecessary, and will be difficult to always satisfy in heavily loaded environment with thousands of threads. It is a quasi real time constraint in a non real time environment, where deadlines can't satisfied.

----------System.out:(43/2706)----------
test SleepWithDuration.testInterruptSleep(): success
test SleepWithDuration.testSleep(): failure
java.lang.AssertionError: Duration 4261ms, expected <= 4000ms expected [true] but found [false]
at org.testng.Assert.fail(Assert.java:99)
at org.testng.Assert.failNotEquals(Assert.java:1037)
at org.testng.Assert.assertTrue(Assert.java:45)
at SleepWithDuration.expectDuration(SleepWithDuration.java:123)
at SleepWithDuration.testSleep(SleepWithDuration.java:46)