testsuite: cover flux overlay trace

Problem: flux overlay trace has no test coverage

Add a sharness test.

Author: garlick

t/Makefile.am

@@ -253,6 +253,7 @@ TESTSCRIPTS = \
 	t3307-system-leafcrash.t \
 	t3308-system-torpid.t \
 	t3309-system-reconnect.t \
+	t3400-overlay-trace.t \
 	lua/t0001-send-recv.t \
 	lua/t0002-rpc.t \
 	lua/t0003-events.t \

t/t3400-overlay-trace.t

@@ -0,0 +1,39 @@
+#!/bin/sh
+
+test_description='Test flux overlay trace'
+
+. $(dirname $0)/sharness.sh
+
+test_under_flux 4
+
+waitfile="${SHARNESS_TEST_SRCDIR}/scripts/waitfile.lua"
+
+test_expect_success 'flux overlay trace fails with extra positional argument' '
+	test_must_fail flux overlay trace x y
+'
+test_expect_success 'flux overlay trace fails with unknown argument' '
+	test_must_fail flux overlay trace --not-an-arg
+'
+test_expect_success 'flux overlay trace fails with wrong message type' '
+	test_must_fail flux overlay trace -t foo,bar
+'
+test_expect_success 'reload heartbeat with increased heart rate' '
+	flux module reload heartbeat period=0.2s
+'
+test_expect_success NO_CHAIN_LINT 'start background trace' '
+	flux overlay trace >trace.out &
+	echo $! >trace.pid
+'
+test_expect_success NO_CHAIN_LINT 'heartbeat.pulse event was captured' '
+	$waitfile -t 60 -p heartbeat.pulse trace.out
+'
+test_expect_success NO_CHAIN_LINT 'send one kvs.ping to rank 1' '
+	flux ping -r 1 -c 1 kvs
+'
+test_expect_success NO_CHAIN_LINT 'kvs.ping request/response was captured' '
+	$waitfile -t 60 -c 2 -p kvs.ping trace.out
+'
+test_expect_success NO_CHAIN_LINT 'stop background trace' '
+	kill -15 $(cat trace.pid); wait || true
+'
+test_done