@Test
  public void testGetCurrentTimeUsesSystemClock() {
    IncrementingEnvironmentEdge edge = new IncrementingEnvironmentEdge(1);
    assertEquals(1, edge.currentTime());
    assertEquals(2, edge.currentTime());
    assertEquals(3, edge.currentTime());
    assertEquals(4, edge.currentTime());
  }
Tests that the incrementing environment edge increments time instead of using the default.
hbase-server/src/test/java/org/apache/hadoop/hbase/util/TestIncrementingEnvironmentEdge.java