serve-stale tests false negative

Job #1772976 failed for d4f7963d:

8455I:serve-stale:sending queries for tests 144-145...
8456I:serve-stale:enable responses from authoritative server (143)
8457I:serve-stale:check not in cache longttl.example times out (stale-answer-client-timeout 1.8) (144)
8458I:serve-stale:check not in cache longttl.example comes from authoritative (stale-answer-client-timeout 1.8) (145)
8459I:serve-stale:failed

Both digs completed within a second of each other but only one of the two passed despite the contents matching the expected values which leads me to conclude that dig.out.test145 was still being written when the greps where made.

% ls -lT dig.out.test14[45]
-rw-r--r--@ 1 marka  staff  184  3 Jun 14:42:51 2021 dig.out.test144
-rw-r--r--@ 1 marka  staff  664  3 Jun 14:42:52 2021 dig.out.test145
% 

% grep "status: NOERROR" dig.out.test145
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 46667
% grep "ANSWER: 1," dig.out.test145
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

n=$((n+1))
echo_i "check not in cache longttl.example times out (stale-answer-client-timeout 1.8) ($n)"
ret=0
wait_for_log 3 "longttl.example client timeout, stale answer unavailable" ns3/named.run || ret=1
waitfile() {
    [ -s "$1" ] || return 1
}
retry_quiet 3 waitfile dig.out.test$n || ret=1
grep "connection timed out" dig.out.test$n > /dev/null || ret=1
if [ $ret != 0 ]; then echo_i "failed"; fi
status=$((status+ret))

n=$((n+1))
echo_i "check not in cache longttl.example comes from authoritative (stale-answer-client-timeout 1.8) ($n)"
ret=0
retry_quiet 7 waitfile dig.out.test$n || ret=1
grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
if [ $ret != 0 ]; then echo_i "failed"; fi
status=$((status+ret))