WireMock

I’ve never tried this but since SSE is (as far as I know) just a set of conventions on top of standard HTTP, I think you could send a finite set of events by configuring a stub in the normal way that returns a `text/event-stream` content-type header with the body structured according to the standard.

If you wanted to create delays you could get something approximate by using chunked dribble delay (the main constraint being that you have to set a specific chunk size so unless your messages are equal in size they might get scheduled in multiple chunks)