// update by USER
admin.updateCredential("dimuthu", "password", "topsecret");
//assertTrue(admin.authenticate("dimuthu", "password")); //TO DO
assertFalse(admin.authenticate("dimuthu", "credential"));
try{
admin.updateCredential("dimuthu", "password", "xxx");
TestCase.assertTrue(false);
}catch(Exception ex){
//expected exception
}