This run_test helper sets up a convention that allows
us to give really short tracebacks for errors, and
eventually we can have more control over running
individual tests. (The latter goal has some
complications, since we often intentionally leak
setup in tests.)
We now track our inbound timing events using code in
typing_data.js.
This code may be a little more robust with variations on how
recipients are represented in events, although there are no known
bugs here.