@Test
public void testSleeping() {

    final B2Clock clock = new B2ClockImpl();
    final long beforeMillis = clock.monotonicMillis();
    sleeper.sleepSeconds(1);
    final long afterMillis = clock.monotonicMillis();
    // we should've slept most of a second! (and not thrown)
    assertTrue((afterMillis - beforeMillis) > 900);
}