protected AuthenticationInfo doAuthenticate(AuthenticationToken token) throws AuthenticationException {
                throw ae;
            }
Ensures a non-null <tt>Subject</tt> instance is returned from the authenticate() method after a valid
authentication attempt (i.e. the subclass's doAuthenticate implementation returns a valid, non-null
AuthenticationInfo object).
core/src/test/java/org/apache/shiro/authc/AbstractAuthenticatorTest.java