Why freeradius server says invalid Message-Authenticator which is generated from radtest

I am learning how to use freeradius, the version is v2.1.12. When I run radtest, there is no response from server, I see server side debug message has the following:

Received packet from 127.0.0.1 with invalid Message-Authenticator!  (Shared secret is incorrect.) Dropping packet without response.

Here is radtest command: radtest -x selftest password 127.0.0.1 0 secret

Here is my edit of /etc/freeradius/clients.conf:

client selftest {
     ipaddr = 127.0.0.1
     secret = secret
}

Here is my edit of /etc/freeradius/users:

selftest Cleartext-Password := "password"

Here is the full output from radtest:

radtest -x selftest password 127.0.0.1 0 secret
Sending Access-Request of id 238 to 127.0.0.1 port 1812
        User-Name = "selftest"
        User-Password = "password"
        NAS-IP-Address = 127.0.0.1
        NAS-Port = 0
        Message-Authenticator = 0x00000000000000000000000000000000

Do you see what is wrong?

[UPDATE]
Thanks arran-cudbard-bell, I change to "testing123", it is better, it got reject, but this is better.

Indeed I made some changes in /etc/hosts which could be the reason, it is like this:

127.0.0.1 localhost     <== pre-existed
127.0.0.1 selftest      <== my edit

The reason I add the line is, without it, I cannot even run radtest, I get this error:

# radtest -x -t pap localhost password 127.0.0.1 0 testing123
radclient:: Failed to find IP address for test-server
radclient: Nothing to send.

You know how to solve it?