@Override
  public void init(LogWriter systemLogger, LogWriter securityLogger)
      throws AuthenticationFailedException {
    user = System.getProperty(TEST_UPDATABLE_USER, "");
    waitTime = Long.getLong(TEST_UPDATABLE_WAIT_TIME, 0L);
  }
this is used in conjunction with ExpirableSecurityManager. It will create a new set of
credentials every time getCredentials are called, and they will always be authenticated
and authorized by the ExpirableSecurityManager.

make sure reset is called after each test to clean things up.
geode-junit/src/main/java/org/apache/geode/security/UpdatableUserAuthInitialize.java