Trying to force a web application monitoring alert

Hi,  We were trying to test an alert for a web application monitor.

We changed the IP of Web URL (in the hosts file) on both of our scom servers who are the only machines in the monitoring pool that is assigned.

Host file  example

ip.address.ofsite.thatreturns404      companyname.accesscontrol.windows.net

We were monitoring Azure ACS with the following URL

https://companyname.accesscontrol.windows.net/along withsome/parameters/etc

The view and validate tests of the actual monitor failed and returned error code 404 but the alert never fired in SCOM until the web site actually went down a couple hours later.

Any ideas why our attempt to fake out scom and force a test alert did not work?

Thanks Lance