“The test form is only available for requests from the local machine.”

You can work around this issue by modifying your web.config to include these nodes:

<configuration>
    <system.web>
     <webServices>
        <protocols>
            <add name="HttpGet"/>
            <add name="HttpPost"/>
        </protocols>
    </webServices>
    </system.web>
</configuration>

This will allow you to visit the .asmx web service via your browser. You can then invoke the web services right in your browser, pass arguments, and view the results.