@Test
public void testCdf() {

  Exponential dist = new Exponential(5.0, RandomUtils.getRandom());
  for (int i = 0; i < 1000; i++) {
    double x = i / 50.0;
    assertEquals(1 - Math.exp(-x * 5.0), dist.cdf(x), 1.0e-9);
  }
}