BT Test Login

[#1]

I have tried the help pages but couldn't find it.
What are the BT Test Login details for troubleshooting a Plusnet connection.
The first step appears to be
    Username: bt_test_user@startup_domain
    Password: (leave blank)
and the second step
  Username: bt_test_user@ispdomain.com
    Password: (leave blank)
I got that from https://help.fasthosts.co.uk/app/answers/detail/a_id/1598/~/testing-your-connection-to-bt%27s-radius...
If the above is correct what is put in the second test for  username

[#2]

Almost right - the basic test is bt_test@startup_domain - if you are diagnosing connection issues and that connects, you can access http://www.bt.net/digitaldemo/ but nothing else.
The ISP specific test is bt_test_user@ispdomain.com, so for PlusNet it would be bt_test_user@plusdsl.net
If you mean for Test 3 on the BT speed test, AFAIR the user name is speedtest@speedtest_domain
None of these requires a password, although some routers do. If yours does, just use something like "adsl1234" or your own connection password should also work.