My application is making an XHR POST that I need to either fail on purpose or be skipped completely. The test is to run a scenario where the service I am requesting is unavailable.

This has to be done in the browser, I don't have the access to make a coding change to do this, nor the firewall. This asnyc XHR call will happen on transition from one tile to another in a single page web app, along with other XHR calls

So far I have used firebug's XHR breakpoint, but I have already got a successfull response when the breakpoint kicks in.

Any other ways to do this?