diff --git a/bin/tests/system/serve-stale/ns1/named1.conf.in b/bin/tests/system/serve-stale/ns1/named1.conf.in
index be3551aae9..c29bcd7a44 100644
--- a/bin/tests/system/serve-stale/ns1/named1.conf.in
+++ b/bin/tests/system/serve-stale/ns1/named1.conf.in
@@ -30,6 +30,7 @@ options {
 	max-stale-ttl 3600;
 	stale-answer-ttl 2;
 	stale-answer-enable yes;
+	servfail-ttl 0;
 };
 
 zone "." {
diff --git a/bin/tests/system/serve-stale/ns1/named2.conf.in b/bin/tests/system/serve-stale/ns1/named2.conf.in
index 7ec265e631..a41f07b140 100644
--- a/bin/tests/system/serve-stale/ns1/named2.conf.in
+++ b/bin/tests/system/serve-stale/ns1/named2.conf.in
@@ -27,9 +27,10 @@ options {
 	listen-on { 10.53.0.1; };
 	listen-on-v6 { none; };
 	recursion yes;
-	max-stale-ttl 45;
+	max-stale-ttl 20;
 	stale-answer-ttl 3;
 	stale-answer-enable yes;
+	servfail-ttl 0;
 };
 
 zone "." {
diff --git a/bin/tests/system/serve-stale/tests.sh b/bin/tests/system/serve-stale/tests.sh
index 07f28def52..252eeab994 100755
--- a/bin/tests/system/serve-stale/tests.sh
+++ b/bin/tests/system/serve-stale/tests.sh
@@ -14,75 +14,68 @@ SYSTEMTESTTOP=..
 
 RNDCCMD="$RNDC -c $SYSTEMTESTTOP/common/rndc.conf -p ${CONTROLPORT} -s"
 
+# wait up to ten seconds to ensure that a file has been written
+waitfile () {
+    for try in 0 1 2 3 4 5 6 7 8 9; do
+        [ -s "$1" ] && break
+        sleep 1
+    done
+}
+
 status=0
 n=0
 
-#echo_i "check ans.pl server ($n)"
-#$DIG -p ${PORT} @10.53.0.2 example NS
-#$DIG -p ${PORT} @10.53.0.2 example SOA
-#$DIG -p ${PORT} @10.53.0.2 ns.example A
-#$DIG -p ${PORT} @10.53.0.2 ns.example AAAA
-#$DIG -p ${PORT} @10.53.0.2 txt enable
-#$DIG -p ${PORT} @10.53.0.2 txt disable
-#$DIG -p ${PORT} @10.53.0.2 ns.example AAAA
-#$DIG -p ${PORT} @10.53.0.2 txt enable
-#$DIG -p ${PORT} @10.53.0.2 ns.example AAAA
-#$DIG -p ${PORT} @10.53.0.2 data.example TXT
-#$DIG -p ${PORT} @10.53.0.2 nodata.example TXT
-#$DIG -p ${PORT} @10.53.0.2 nxdomain.example TXT
-#$DIG -p ${PORT} @10.53.0.2 othertype.example CAA
-
 #
 # First test server with serve-stale options set.
 #
 echo_i "test server with serve-stale options set"
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache longttl.example ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.1 longttl.example TXT > dig.out.test$n
 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=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache data.example ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
 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=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache othertype.example ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$n
 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=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache nodata.example ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache nxdomain.example ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$n
 grep "status: NXDOMAIN" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "verify prime cache statistics ($n)"
 ret=0
 rm -f ns1/named.stats
@@ -97,31 +90,42 @@ grep "2 TXT" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 !TXT" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 NXDOMAIN" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "disable responses from authoritative server ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.2 txt disable  > dig.out.test$n
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "TXT.\"0\"" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-sleep 2
-
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale status' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale status > rndc.out.test$n 2>&1 || ret=1
 grep '_default: on (stale-answer-ttl=2 max-stale-ttl=3600)' rndc.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+sleep 2
+
+echo_i "sending queries for tests $((n+1))-$((n+4))..."
+$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$((n+1)) &
+$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$((n+2)) &
+$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$((n+3)) &
+$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$((n+4))
+
+# ensure all files have been written before proceeding
+waitfile dig.out.test$((n+1))
+waitfile dig.out.test$((n+2))
+waitfile dig.out.test$((n+3))
+waitfile dig.out.test$((n+4))
+
+n=$((n+1))
 echo_i "check stale data.example ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "data\.example\..*2.*IN.*TXT.*A text record with a 2 second ttl" dig.out.test$n > /dev/null || ret=1
@@ -135,39 +139,36 @@ awk '/; stale/ { x=$0; getline; print x, $0}' ns1/named_dump.db.test$n |
 awk '/; answer/ { x=$0; getline; print x, $0}' ns1/named_dump.db.test$n |
     grep "; answer longttl\.example.*A text record with a 600 second ttl" > /dev/null 2>&1 || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale othertype.example ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "othertype\.example\..*2.*IN.*CAA.*0.*issue" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale nodata.example ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*2.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale nxdomain.example ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$n
 grep "status: NXDOMAIN" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*2.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "verify stale cache statistics ($n)"
 ret=0
 rm -f ns1/named.stats
@@ -183,189 +184,211 @@ grep "1 #Others" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 #TXT" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 #!TXT" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 #NXDOMAIN" ns1/named.stats.$n.cachedb > /dev/null || ret=1
-status=`expr $status + $ret`
+status=$((status+ret))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "running 'rndc serve-stale off' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale off || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale status' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale status > rndc.out.test$n 2>&1 || ret=1
 grep '_default: off (rndc) (stale-answer-ttl=2 max-stale-ttl=3600)' rndc.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+echo_i "sending queries for tests $((n+1))-$((n+4))..."
+$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$((n+1)) &
+$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$((n+2)) &
+$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$((n+3)) &
+$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$((n+4))
+
+# ensure all files have been written before proceeding
+waitfile dig.out.test$((n+1))
+waitfile dig.out.test$((n+2))
+waitfile dig.out.test$((n+3))
+waitfile dig.out.test$((n+4))
+
+n=$((n+1))
 echo_i "check stale data.example (serve-stale off) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
-if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale othertype.example (serve-stale off) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale nodata.example (serve-stale off) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale nxdomain.example (serve-stale off) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "running 'rndc serve-stale on' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale on || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale status' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale status > rndc.out.test$n 2>&1 || ret=1
 grep '_default: on (rndc) (stale-answer-ttl=2 max-stale-ttl=3600)' rndc.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+echo_i "sending queries for tests $((n+1))-$((n+4))..."
+$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$((n+1)) &
+$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$((n+2)) &
+$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$((n+3)) &
+$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$((n+4))
+
+# ensure all files have been written before proceeding
+waitfile dig.out.test$((n+1))
+waitfile dig.out.test$((n+2))
+waitfile dig.out.test$((n+3))
+waitfile dig.out.test$((n+4))
+
+n=$((n+1))
 echo_i "check stale data.example (serve-stale on) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "data\.example\..*2.*IN.*TXT.*A text record with a 2 second ttl" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale othertype.example (serve-stale on) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "othertype\.example\..*2.*IN.*CAA.*0.*issue" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale nodata.example (serve-stale on) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*2.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale nxdomain.example (serve-stale on) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$n
 grep "status: NXDOMAIN" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*2.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "running 'rndc serve-stale off' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale off || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "running 'rndc serve-stale reset' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale reset || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale status' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale status > rndc.out.test$n 2>&1 || ret=1
 grep '_default: on (stale-answer-ttl=2 max-stale-ttl=3600)' rndc.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+echo_i "sending queries for tests $((n+1))-$((n+4))..."
+$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$((n+1)) &
+$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$((n+2)) &
+$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$((n+3)) &
+$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$((n+4))
+
+# ensure all files have been written before proceeding
+waitfile dig.out.test$((n+1))
+waitfile dig.out.test$((n+2))
+waitfile dig.out.test$((n+3))
+waitfile dig.out.test$((n+4))
+
+n=$((n+1))
 echo_i "check stale data.example (serve-stale reset) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "data\.example\..*2.*IN.*TXT.*A text record with a 2 second ttl" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale othertype.example (serve-stale reset) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "othertype.example\..*2.*IN.*CAA.*0.*issue" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale nodata.example (serve-stale reset) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*2.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale nxdomain.example (serve-stale reset) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$n
 grep "status: NXDOMAIN" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*2.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "running 'rndc serve-stale off' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale off || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale status' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale status > rndc.out.test$n 2>&1 || ret=1
 grep '_default: off (rndc) (stale-answer-ttl=2 max-stale-ttl=3600)' rndc.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
 #
 # Update named.conf.
@@ -373,29 +396,29 @@ status=`expr $status + $ret`
 #
 echo_i "test server with serve-stale options set, low max-stale-ttl"
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "updating ns1/named.conf ($n)"
 ret=0
 copy_setports ns1/named2.conf.in ns1/named.conf
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "running 'rndc reload' ($n)"
 ret=0
 rndc_reload ns1 10.53.0.1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale status' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale status > rndc.out.test$n 2>&1 || ret=1
-grep '_default: off (rndc) (stale-answer-ttl=3 max-stale-ttl=45)' rndc.out.test$n > /dev/null || ret=1
+grep '_default: off (rndc) (stale-answer-ttl=3 max-stale-ttl=20)' rndc.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "flush cache, re-enable serve-stale and query again ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 flushtree example > rndc.out.test$n.1 2>&1 || ret=1
@@ -404,73 +427,71 @@ $DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale status' ($n)"
 ret=0
 $RNDCCMD 10.53.0.1 serve-stale status > rndc.out.test$n 2>&1 || ret=1
-grep '_default: on (rndc) (stale-answer-ttl=3 max-stale-ttl=45)' rndc.out.test$n > /dev/null || ret=1
+grep '_default: on (rndc) (stale-answer-ttl=3 max-stale-ttl=20)' rndc.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "enable responses from authoritative server ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.2 txt enable  > dig.out.test$n
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "TXT.\"1\"" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-sleep 2
-
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache longttl.example (low max-stale-ttl) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.1 longttl.example TXT > dig.out.test$n
 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=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache data.example (low max-stale-ttl) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
 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=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache othertype.example (low max-stale-ttl) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$n
 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=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache nodata.example (low max-stale-ttl) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache nxdomain.example (low max-stale-ttl) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$n
 grep "status: NXDOMAIN" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "verify prime cache statistics (low max-stale-ttl) ($n)"
 ret=0
 rm -f ns1/named.stats
@@ -484,61 +505,69 @@ grep "2 TXT" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 Others" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 !TXT" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 NXDOMAIN" ns1/named.stats.$n.cachedb > /dev/null || ret=1
-status=`expr $status + $ret`
+status=$((status+ret))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "disable responses from authoritative server ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.2 txt disable  > dig.out.test$n
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "TXT.\"0\"" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
 sleep 2
 
-n=`expr $n + 1`
+echo_i "sending queries for tests $((n+1))-$((n+4))..."
+$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$((n+1)) &
+$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$((n+2)) &
+$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$((n+3)) &
+$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$((n+4))
+
+# ensure all files have been written before proceeding
+waitfile dig.out.test$((n+1))
+waitfile dig.out.test$((n+2))
+waitfile dig.out.test$((n+3))
+waitfile dig.out.test$((n+4))
+
+n=$((n+1))
 echo_i "check stale data.example (low max-stale-ttl) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "data\.example\..*3.*IN.*TXT.*A text record with a 2 second ttl" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale othertype.example (low max-stale-ttl) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "othertype\.example\..*3.*IN.*CAA.*0.*issue" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale nodata.example (low max-stale-ttl) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*3.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check stale nxdomain.example (low max-stale-ttl) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$n
 grep "status: NXDOMAIN" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*3.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "verify stale cache statistics (low max-stale-ttl) ($n)"
 ret=0
 rm -f ns1/named.stats
@@ -555,71 +584,77 @@ grep "1 #Others" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 #!TXT" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 #NXDOMAIN" ns1/named.stats.$n.cachedb > /dev/null || ret=1
 
-status=`expr $status + $ret`
+status=$((status+ret))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 
-sleep 2
+echo_i "sending queries for tests $((n+1))-$((n+4))..."
+$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$((n+1)) &
+$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$((n+2)) &
+$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$((n+3)) &
+$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$((n+4))
 
-n=`expr $n + 1`
+# ensure all files have been written before proceeding
+waitfile dig.out.test$((n+1))
+waitfile dig.out.test$((n+2))
+waitfile dig.out.test$((n+3))
+waitfile dig.out.test$((n+4))
+
+n=$((n+1))
 echo_i "check ancient data.example (low max-stale-ttl) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 data.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check ancient othertype.example (low max-stale-ttl) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 othertype.example CAA > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check ancient nodata.example (low max-stale-ttl) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nodata.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check ancient nxdomain.example (low max-stale-ttl) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.1 nxdomain.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
 #
 # Now test server with no serve-stale options set.
 #
 echo_i "test server with no serve-stale options set"
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "enable responses from authoritative server ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.2 txt enable  > dig.out.test$n
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "TXT.\"1\"" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache longttl.example (max-stale-ttl default) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.3 longttl.example TXT > dig.out.test$n
 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=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache data.example (max-stale-ttl default) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.3 data.example TXT > dig.out.test$n
@@ -627,9 +662,9 @@ grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "data\.example\..*2.*IN.*TXT.*A text record with a 2 second ttl" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache othertype.example (max-stale-ttl default) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.3 othertype.example CAA > dig.out.test$n
@@ -637,9 +672,9 @@ grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "othertype\.example\..*2.*IN.*CAA.*0.*issue" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache nodata.example (max-stale-ttl default) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.3 nodata.example TXT > dig.out.test$n
@@ -647,9 +682,9 @@ grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*2.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache nxdomain.example (max-stale-ttl default) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.3 nxdomain.example TXT > dig.out.test$n
@@ -657,9 +692,9 @@ grep "status: NXDOMAIN" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*2.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "verify prime cache statistics (max-stale-ttl default) ($n)"
 ret=0
 rm -f ns3/named.stats
@@ -673,65 +708,73 @@ grep "2 TXT" ns3/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 Others" ns3/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 !TXT" ns3/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 NXDOMAIN" ns3/named.stats.$n.cachedb > /dev/null || ret=1
-status=`expr $status + $ret`
+status=$((status+ret))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "disable responses from authoritative server ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.2 txt disable  > dig.out.test$n
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "TXT.\"0\"" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-sleep 2
-
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale status' ($n)"
 ret=0
 $RNDCCMD 10.53.0.3 serve-stale status > rndc.out.test$n 2>&1 || ret=1
 grep '_default: off (stale-answer-ttl=1 max-stale-ttl=604800)' rndc.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+sleep 2
+
+echo_i "sending queries for tests $((n+1))-$((n+4))..."
+$DIG -p ${PORT} @10.53.0.3 data.example TXT > dig.out.test$((n+1)) &
+$DIG -p ${PORT} @10.53.0.3 othertype.example CAA > dig.out.test$((n+2)) &
+$DIG -p ${PORT} @10.53.0.3 nodata.example TXT > dig.out.test$((n+3)) &
+$DIG -p ${PORT} @10.53.0.3 nxdomain.example TXT > dig.out.test$((n+4))
+
+# ensure all files have been written before proceeding
+waitfile dig.out.test$((n+1))
+waitfile dig.out.test$((n+2))
+waitfile dig.out.test$((n+3))
+waitfile dig.out.test$((n+4))
+
+n=$((n+1))
 echo_i "check fail of data.example (max-stale-ttl default) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.3 data.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check fail of othertype.example (max-stale-ttl default) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.3 othertype.example CAA > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check fail of nodata.example (max-stale-ttl default) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.3 nodata.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check fail of nxdomain.example (max-stale-ttl default) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.3 nxdomain.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "verify stale cache statistics (max-stale-ttl default) ($n)"
 ret=0
 rm -f ns3/named.stats
@@ -748,88 +791,98 @@ grep "1 #Others" ns3/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 #!TXT" ns3/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 #NXDOMAIN" ns3/named.stats.$n.cachedb > /dev/null || ret=1
 
-status=`expr $status + $ret`
+status=$((status+ret))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale on' ($n)"
 ret=0
 $RNDCCMD 10.53.0.3 serve-stale on > rndc.out.test$n 2>&1 || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale status' ($n)"
 ret=0
 $RNDCCMD 10.53.0.3 serve-stale status > rndc.out.test$n 2>&1 || ret=1
 grep '_default: on (rndc) (stale-answer-ttl=1 max-stale-ttl=604800)' rndc.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+sleep 2
+
+echo_i "sending queries for tests $((n+1))-$((n+4))..."
+$DIG -p ${PORT} @10.53.0.3 data.example TXT > dig.out.test$((n+1)) &
+$DIG -p ${PORT} @10.53.0.3 othertype.example CAA > dig.out.test$((n+2)) &
+$DIG -p ${PORT} @10.53.0.3 nodata.example TXT > dig.out.test$((n+3)) &
+$DIG -p ${PORT} @10.53.0.3 nxdomain.example TXT > dig.out.test$((n+4))
+
+# ensure all files have been written before proceeding
+waitfile dig.out.test$((n+1))
+waitfile dig.out.test$((n+2))
+waitfile dig.out.test$((n+3))
+waitfile dig.out.test$((n+4))
+
+n=$((n+1))
 echo_i "check data.example (max-stale-ttl default) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.3 data.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "data\.example\..*1.*IN.*TXT.*A text record with a 2 second ttl" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check othertype.example (max-stale-ttl default) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.3 othertype.example CAA > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "example\..*1.*IN.*CAA.*0.*issue" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check nodata.example (max-stale-ttl default) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.3 nodata.example TXT > dig.out.test$n
 grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*1.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check nxdomain.example (max-stale-ttl default) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.3 nxdomain.example TXT > dig.out.test$n
 grep "status: NXDOMAIN" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*1.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
 #
 # Now test server with serve-stale disabled.
 #
 echo_i "test server with serve-stale disabled"
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "enable responses from authoritative server ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.2 txt enable  > dig.out.test$n
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "TXT.\"1\"" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache longttl.example (serve-stale disabled) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.4 longttl.example TXT > dig.out.test$n
 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=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache data.example (serve-stale disabled) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.4 data.example TXT > dig.out.test$n
@@ -837,9 +890,9 @@ grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "data\.example\..*2.*IN.*TXT.*A text record with a 2 second ttl" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache othertype.example (serve-stale disabled) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.4 othertype.example CAA > dig.out.test$n
@@ -847,9 +900,9 @@ grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "othertype\.example\..*2.*IN.*CAA.*0.*issue" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache nodata.example (serve-stale disabled) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.4 nodata.example TXT > dig.out.test$n
@@ -857,9 +910,9 @@ grep "status: NOERROR" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*2.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "prime cache nxdomain.example (serve-stale disabled) ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.4 nxdomain.example TXT > dig.out.test$n
@@ -867,9 +920,9 @@ grep "status: NXDOMAIN" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 grep "example\..*2.*IN.*SOA" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "verify prime cache statistics (serve-stale disabled) ($n)"
 ret=0
 rm -f ns4/named.stats
@@ -883,65 +936,73 @@ grep "2 TXT" ns4/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 Others" ns4/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 !TXT" ns4/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 NXDOMAIN" ns4/named.stats.$n.cachedb > /dev/null || ret=1
-status=`expr $status + $ret`
+status=$((status+ret))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "disable responses from authoritative server ($n)"
 ret=0
 $DIG -p ${PORT} @10.53.0.2 txt disable  > dig.out.test$n
 grep "ANSWER: 1," dig.out.test$n > /dev/null || ret=1
 grep "TXT.\"0\"" dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-sleep 2
-
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check 'rndc serve-stale status' ($n)"
 ret=0
 $RNDCCMD 10.53.0.4 serve-stale status > rndc.out.test$n 2>&1 || ret=1
 grep '_default: off (stale-answer-ttl=1 max-stale-ttl=604800)' rndc.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+sleep 2
+
+echo_i "sending queries for tests $((n+1))-$((n+4))..."
+$DIG -p ${PORT} @10.53.0.4 data.example TXT > dig.out.test$((n+1)) &
+$DIG -p ${PORT} @10.53.0.4 othertype.example CAA > dig.out.test$((n+2)) &
+$DIG -p ${PORT} @10.53.0.4 nodata.example TXT > dig.out.test$((n+3)) &
+$DIG -p ${PORT} @10.53.0.4 nxdomain.example TXT > dig.out.test$((n+4))
+
+# ensure all files have been written before proceeding
+waitfile dig.out.test$((n+1))
+waitfile dig.out.test$((n+2))
+waitfile dig.out.test$((n+3))
+waitfile dig.out.test$((n+4))
+
+n=$((n+1))
 echo_i "check fail of data.example (serve-stale disabled) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.4 data.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check fail of othertype.example (serve-stale disabled) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.4 othertype.example CAA > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check fail of nodata.example (serve-stale disabled) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.4 nodata.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "check fail of nxdomain.example (serve-stale disabled) ($n)"
 ret=0
-$DIG -p ${PORT} @10.53.0.4 nxdomain.example TXT > dig.out.test$n
 grep "status: SERVFAIL" dig.out.test$n > /dev/null || ret=1
 grep "ANSWER: 0," dig.out.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "verify stale cache statistics (serve-stale disabled) ($n)"
 ret=0
 rm -f ns4/named.stats
@@ -957,11 +1018,11 @@ grep "1 #TXT" ns4/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 #Others" ns4/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 #!TXT" ns4/named.stats.$n.cachedb > /dev/null || ret=1
 grep "1 #NXDOMAIN" ns4/named.stats.$n.cachedb > /dev/null || ret=1
-status=`expr $status + $ret`
+status=$((status+ret))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 
 # Dump the cache.
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "dump the cache (serve-stale disabled) ($n)"
 ret=0
 $RNDCCMD 10.53.0.4 dumpdb -cache > rndc.out.test$n 2>&1 || ret=1
@@ -971,7 +1032,7 @@ for i in 0 1 2 3 4 5 6 7 8 9; do
 	if [ $done != 1 ]; then sleep 1; fi
 done
 if [ $done != 1 ]; then ret=1; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 
 echo_i "stop ns4"
@@ -986,20 +1047,18 @@ LASTWEEK=`TZ=UTC perl -e 'my $now = time();
         my ($s, $m, $h, $d, $mo, $y) = (localtime($fiveMinutesAgo))[0, 1, 2, 3, 4, 5];
         printf("%04d%02d%02d%02d%02d%02d", $y+1900, $mo+1, $d, $h, $m, $s);'`
 
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "mock the cache date to $LASTWEEK (serve-stale disabled) ($n)"
 ret=0
 sed -E "s/DATE [0-9]{14}/DATE $LASTWEEK/g" ns4/named_dump4.db > ns4/named_dumpdb4.db.out || ret=1
 cp ns4/named_dumpdb4.db.out ns4/named_dumpdb4.db
 if [ $ret != 0 ]; then echo_i "failed"; fi
-status=`expr $status + $ret`
+status=$((status+ret))
 
 echo_i "start ns4"
 $PERL $SYSTEMTESTTOP/start.pl --noclean --restart --port ${PORT} serve-stale ns4
 
-sleep 2
-
-n=`expr $n + 1`
+n=$((n+1))
 echo_i "verify ancient cache statistics (serve-stale disabled) ($n)"
 ret=0
 rm -f ns4/named.stats
@@ -1013,7 +1072,7 @@ grep "#TXT" ns4/named.stats.$n.cachedb > /dev/null && ret=1
 grep "#Others" ns4/named.stats.$n.cachedb > /dev/null && ret=1
 grep "#!TXT" ns4/named.stats.$n.cachedb > /dev/null && ret=1
 grep "#NXDOMAIN" ns4/named.stats.$n.cachedb > /dev/null && ret=1
-status=`expr $status + $ret`
+status=$((status+ret))
 if [ $ret != 0 ]; then echo_i "failed"; fi
 
 echo_i "exit status: $status"