Particularly when testing, a quick way to assess Instana's ability is to allow a component to go offline. An offline event is not necessarily a problem (Orchestrated environments spin up/down frequently), but you may want to add additional rules for offline hosts or key containers.
An offline alert might be generated typically for :-
entity.selfType:host or entity.selfType:container
Of course in a production scenario, the drop in requests would fire as an issue if one of the key components went offline - this normally just surfaces when you wish to manually test.