@Test
public void testFSLeakInObtainSystemTokensForUser() throws Exception{

  Credentials credentials = new Credentials();
  String user = "test";
  int oldCounter = MyFS.getInstanceCounter();
  delegationTokenRenewer.obtainSystemTokensForUser(user, credentials);
  delegationTokenRenewer.obtainSystemTokensForUser(user, credentials);
  delegationTokenRenewer.obtainSystemTokensForUser(user, credentials);
  Assert.assertEquals(oldCounter, MyFS.getInstanceCounter());
}