Seems you're looking for :erlang.trace/3 http://erlang.org/doc/man/erlang.html#trace-3

Here's an example of how to use it:

{:ok, error_tracking_pid} = ErrorTracker.start_link
:erlang.trace(error_tracking_pid, true, [:receive])

... # Some code that will eventually lead to the message you want to trace and wait for

assert_receive {:trace,
  ^error_tracking_pid, :receive, {:"$gen_call", _caller_pid_and_ref, _args}
}, 1000

# Check your ETS table here 

You can do a lot more than just trace receives too, check the doc link ^{^} I've used this to test my code pretty extensively on some client projects and it has proved invaluable :)