Are you using RSpec? If so, you can override the functionality of the EventPusher's publish method inside the test itself, like this:
EventPusher.any_instance.stub(:publish)
The above code replaces the original publish method with an empty method that returns nil. The method still exists and will still be called, but it just won't do anything within the scope of your tests.
If other code is expecting the publish method to return something, such as 'true' to indicate success, then you can add the following:
EventPusher.any_instance.stub(:publish).and_return(true)
Or, if you'd prefer to override the PusherGem's static trigger method, then use this slightly different syntax:
PusherGem.stub!(:trigger)
or
PusherGem.stub!(:trigger).and_return("something here, perhaps?")