@Test
  public void testColdStart() {
    final PhiAccrualDetector coldStartPhi =
        new PhiAccrualDetector(30, 10 * sec, (long) (0.2 * sec), 60, fixedDetector);
    long[] interval = new long[] {sec, sec, sec};
    List<AbstractHeartbeatSample> history = fromInterval(interval, 21 * sec);
    Assert.assertFalse(fixedDetector.isAvailable(id, history));
    Assert.assertFalse(coldStartPhi.isAvailable(id, history));
  }
If the Phi detector haven't received enough samples its behavior will fall back to Fix detector
iotdb-core/confignode/src/test/java/org/apache/iotdb/confignode/manager/load/cache/detector/DetectorTest.java