@Test
public void testTokenRenewerInvalidReturn() throws Exception {

  DelegationTokenToRenew mockDttr = mock(DelegationTokenToRenew.class);
  mockDttr.expirationDate = 0;
  delegationTokenRenewer.setTimerForTokenRenewal(mockDttr);
  assertNull(mockDttr.timerTask);
  mockDttr.expirationDate = -1;
  delegationTokenRenewer.setTimerForTokenRenewal(mockDttr);
  assertNull(mockDttr.timerTask);
  mockDttr.expirationDate = System.currentTimeMillis() - 1;
  delegationTokenRenewer.setTimerForTokenRenewal(mockDttr);
  assertNull(mockDttr.timerTask);
}