Authorize.net ARB API test endpoint not working or is it me?

This is a quick one. I am trying to test an Automatic Recurring Billing (Auth.net's recurring payment API) script which accesses their endpoints.

The trouble is I keep getting this response from their test endpoint when I request with nothing sent http://ift.tt/1lOlaxX :

The page cannot be displayed because an internal server error has occurred.

And this is what I get from their live endpoint http://ift.tt/1qTmGM7 with nothing sent:

<ErrorResponse>
    <messages>
        <resultCode>Error</resultCode>
        <message>
            <code>E00002</code>
            <text>The content-type specified is not supported.</text>
        </message>
    </messages>
</ErrorResponse>

Is their test api broken? As far as I know they should behave identically.