public Set<String> getExpiredUsers() {
    return expired_users;
  }
this is a test security manager that will authenticate credentials when username matches the
password. It will authorize all operations. It keeps a list of expired users, and will throw
AuthenticationExpiredException if the user is in that list. This security manager is usually used
with UpdatableUserAuthInitialize.

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