Stopping an Erlang supervisor?

Question

I'm attempting to test a piece of my application that comprises a supervisor and two (different) workers. I'm using eunit, so in my setup and cleanup, I've got:

setup() ->
    {ok, Pid} = foo_sup:start_link(),
    Pid.

cleanup(Pid) ->
    exit(Pid, kill).

foo_sup:start_link/0 is defined as:

start_link() ->
    supervisor:start_link({local, ?MODULE}, ?MODULE, []).

However, when my tests run, I get {badmatch,{error,{already_started,<0.188.0>}}}, which implies that my supervisor is still running.

How do I:

1. signal a supervisor to stop itself and all of its children?
2. wait for that to complete?

Answer 1

1. Send the shutdown signal to make the supervisor kill its children and exit:

   exit(Pid, shutdown).
   

   You may have to unlink the process from your test first.

2. Monitor the process, to wait for it to exit:

   Ref = monitor(process, Pid),
   receive
       {'DOWN', Ref, process, Pid, _Reason} ->
           ok
   after 1000 ->
           error(exit_timeout)
   end.