That is a fair request.  You could edit main.rs and add after line 123 (at the end of the for loop) this line:

	thread::sleep(std::time::Duration::new(0, 100));

Then it will wait 100ms between tests.  But tests that do multiple messages in a row won't have waits between those.

You could instead try editing connection.rs and add this at the top of send_message() (to wait before every send).

Let me know if those help.