diff --git a/usr.bin/renice/renice.c b/usr.bin/renice/renice.c
index 890d7043ebbd..42e93cce240e 100644
--- a/usr.bin/renice/renice.c
+++ b/usr.bin/renice/renice.c
@@ -1,194 +1,194 @@
 /*-
  * SPDX-License-Identifier: BSD-3-Clause
  *
  * Copyright (c) 1983, 1989, 1993
  *	The Regents of the University of California.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
 
 #ifndef lint
 static const char copyright[] =
 "@(#) Copyright (c) 1983, 1989, 1993\n\
 	The Regents of the University of California.  All rights reserved.\n";
 #endif /* not lint */
 
 #if 0
 #ifndef lint
 static char sccsid[] = "@(#)renice.c	8.1 (Berkeley) 6/9/93";
 #endif /* not lint */
 #endif
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/resource.h>
 
 #include <err.h>
 #include <errno.h>
 #include <limits.h>
 #include <pwd.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 static int	donice(int, int, int, bool);
 static int	getnum(const char *, const char *, int *);
 static void	usage(void);
 
 /*
  * Change the priority (nice) of processes
  * or groups of processes which are already
  * running.
  */
 int
 main(int argc, char *argv[])
 {
 	struct passwd *pwd;
 	bool havedelim = false, haveprio = false, incr = false;
 	int errs = 0, prio = 0, who = 0, which = PRIO_PROCESS;
 
 	for (argc--, argv++; argc > 0; argc--, argv++) {
 		if (!havedelim) {
 			/* can occur at any time prior to delimiter */
 			if (strcmp(*argv, "-g") == 0) {
 				which = PRIO_PGRP;
 				continue;
 			}
 			if (strcmp(*argv, "-u") == 0) {
 				which = PRIO_USER;
 				continue;
 			}
 			if (strcmp(*argv, "-p") == 0) {
 				which = PRIO_PROCESS;
 				continue;
 			}
 			if (strcmp(*argv, "--") == 0) {
 				havedelim = true;
 				continue;
 			}
 			if (strcmp(*argv, "-n") == 0) {
 				/* may occur only once, prior to priority */
-				if (haveprio || incr)
+				if (haveprio || incr || argc < 2)
 					usage();
 				incr = true;
 				(void)argc--, argv++;
 				/* fall through to priority */
 			}
 		}
 		if (!haveprio) {
 			/* must occur exactly once, prior to target */
 			if (getnum("priority", *argv, &prio))
 				return (1);
 			haveprio = true;
 			continue;
 		}
 		if (which == PRIO_USER) {
 			if ((pwd = getpwnam(*argv)) != NULL)
 				who = pwd->pw_uid;
 			else if (getnum("uid", *argv, &who)) {
 				errs++;
 				continue;
 			} else if (who < 0) {
 				warnx("%s: bad value", *argv);
 				errs++;
 				continue;
 			}
 		} else {
 			if (getnum("pid", *argv, &who)) {
 				errs++;
 				continue;
 			}
 			if (who < 0) {
 				warnx("%s: bad value", *argv);
 				errs++;
 				continue;
 			}
 		}
 		errs += donice(which, who, prio, incr);
 	}
 	if (!haveprio)
 		usage();
 	exit(errs != 0);
 }
 
 static int
 donice(int which, int who, int prio, bool incr)
 {
 	int oldprio;
 
 	errno = 0;
 	oldprio = getpriority(which, who);
 	if (oldprio == -1 && errno) {
 		warn("%d: getpriority", who);
 		return (1);
 	}
 	if (incr)
 		prio = oldprio + prio;
 	if (prio > PRIO_MAX)
 		prio = PRIO_MAX;
 	if (prio < PRIO_MIN)
 		prio = PRIO_MIN;
 	if (setpriority(which, who, prio) < 0) {
 		warn("%d: setpriority", who);
 		return (1);
 	}
 	fprintf(stderr, "%d: old priority %d, new priority %d\n", who,
 	    oldprio, prio);
 	return (0);
 }
 
 static int
 getnum(const char *com, const char *str, int *val)
 {
 	long v;
 	char *ep;
 
 	errno = 0;
 	v = strtol(str, &ep, 10);
 	if (v < INT_MIN || v > INT_MAX || errno == ERANGE) {
 		warnx("%s argument %s is out of range.", com, str);
 		return (1);
 	}
 	if (ep == str || *ep != '\0' || errno != 0) {
 		warnx("%s argument %s is invalid.", com, str);
 		return (1);
 	}
 
 	*val = (int)v;
 	return (0);
 }
 
 static void
 usage(void)
 {
 	fprintf(stderr, "%s\n%s\n",
 "usage: renice priority [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]",
 "       renice -n increment [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]");
 	exit(1);
 }
diff --git a/usr.bin/renice/tests/renice_test.sh b/usr.bin/renice/tests/renice_test.sh
old mode 100644
new mode 100755
index 323fe44591c8..feb07a6af825
--- a/usr.bin/renice/tests/renice_test.sh
+++ b/usr.bin/renice/tests/renice_test.sh
@@ -1,169 +1,173 @@
-#!/bin/sh
-#-
-# Copyright (c) 2022 Klara, Inc.
-# All rights reserved.
 #
-# Redistribution and use in source and binary forms, with or without
-# modification, are permitted provided that the following conditions
-# are met:
-# 1. Redistributions of source code must retain the above copyright
-#    notice, this list of conditions and the following disclaimer.
-# 2. Redistributions in binary form must reproduce the above copyright
-#    notice, this list of conditions and the following disclaimer in the
-#    documentation and/or other materials provided with the distribution.
+# Copyright (c) 2022-2023 Klara, Inc.
 #
-# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
-# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
-# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
-# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
-# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
-# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
-# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
-# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
-# SUCH DAMAGE.
+# SPDX-License-Identifier: BSD-2-Clause
 #
 
 # Name of user to use for -u tests when running as root.  Beware that
 # processes owned by that user will be affected by the test.
 TEST_USER=nobody
 
 _renice() {
 	atf_check -o empty -e ignore -s exit:0 renice "$@"
 }
 
-# Set a process's nice number to an absolute value
+atf_check_nice_value() {
+	local pid=$1
+	local nice=$2
+	atf_check test "$(ps -o nice= -p $pid)" -eq "$nice"
+}
+
 atf_test_case renice_abs_pid
+renice_abs_pid_head() {
+	atf_set "descr" "Set a process's nice number to an absolute value"
+}
 renice_abs_pid_body() {
 	local pid nice incr
 	sleep 60 &
 	pid=$!
 	nice="$(ps -o nice= -p $pid)"
 	incr=3
 	_renice $((nice+incr)) $pid
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	kill $pid
 }
 
-# Change a process's nice number by a relative value
 atf_test_case renice_rel_pid
+renice_rel_pid_head() {
+	atf_set "descr" "Change a process's nice number by a relative value"
+}
 renice_rel_pid_body() {
 	local pid nice incr
 	sleep 60 &
 	pid=$!
 	nice="$(ps -o nice= -p $pid)"
 	incr=3
 	_renice -n $incr $pid
 	_renice -p -n $incr $pid
 	_renice -n $incr -p $pid
-	atf_check_equal $((nice+incr+incr+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr+incr+incr))
 	kill $pid
 }
 
-# Set a process group's nice number to an absolute value
 atf_test_case renice_abs_pgid
+renice_abs_pgid_head() {
+	atf_set "descr" "Set a process group's nice number to an absolute value"
+}
 renice_abs_pgid_body() {
 	local pid pgid nice incr
 	# make sure target runs in a different pgrp than ours
 	pid=$(sh -mc "sleep 60 >/dev/null & echo \$!")
 	pgid="$(ps -o pgid= -p $pid)"
 	nice="$(ps -o nice= -p $pid)"
 	incr=3
 	_renice $((nice+incr)) -g $pgid
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	kill $pid
 }
 
-# Change a process group's nice number by a relative value
 atf_test_case renice_rel_pgid
+renice_rel_pgid_head() {
+	atf_set "descr" "Change a process group's nice number by a relative value"
+}
 renice_rel_pgid_body() {
 	local pid pgid nice incr
 	# make sure target runs in a different pgrp than ours
 	pid=$(sh -mc "sleep 60 >/dev/null & echo \$!")
 	pgid="$(ps -o pgid= -p $pid)"
 	nice="$(ps -o nice= -p $pid)"
 	incr=3
 	_renice -g -n $incr $pgid
 	_renice -n $incr -g $pgid
-	atf_check_equal $((nice+incr+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr+incr))
 	kill $pid
 }
 
-# Set a user's processes' nice numbers to an absolute value
 atf_test_case renice_abs_user
 renice_abs_user_head() {
+	atf_set "descr" "Set a user's processes' nice numbers to an absolute value"
 	atf_set "require.user" "root"
 }
 renice_abs_user_body() {
 	local user pid nice incr
 	pid=$(su -m $TEST_USER -c "sleep 60 >/dev/null & echo \$!")
 	nice="$(ps -o nice= -p $pid)"
 	incr=3
 	_renice $((nice+incr)) -u $TEST_USER
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	kill $pid
 }
 
-# Change a user's processes' nice numbers by a relative value
 atf_test_case renice_rel_user
 renice_rel_user_head() {
+	atf_set "descr" "Change a user's processes' nice numbers by a relative value"
 	atf_set "require.user" "root"
 }
 renice_rel_user_body() {
 	local user pid nice incr
 	pid=$(su -m $TEST_USER -c "sleep 60 >/dev/null & echo \$!")
 	nice="$(ps -o nice= -p $pid)"
 	incr=3
 	_renice -u -n $incr $TEST_USER
 	_renice -n $incr -u $TEST_USER
-	atf_check_equal $((nice+incr+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr+incr))
 	kill $pid
 }
 
-# Test various delimiter positions
 atf_test_case renice_delim
+renice_delim_head() {
+	atf_set "descr" "Test various delimiter positions"
+}
 renice_delim_body() {
 	local pid nice incr
 	sleep 60 &
 	pid=$!
 	nice="$(ps -o nice= -p $pid)"
 	incr=0
 	# without -p
 	: $((incr=incr+1))
 	_renice -- $((nice+incr)) $pid
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	: $((incr=incr+1))
 	_renice $((nice+incr)) -- $pid
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	: $((incr=incr+1))
 	_renice $((nice+incr)) $pid --
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	# with -p
 	: $((incr=incr+1))
 	_renice -p -- $((nice+incr)) $pid
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	: $((incr=incr+1))
 	_renice -p $((nice+incr)) -- $pid
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	: $((incr=incr+1))
 	_renice -p $((nice+incr)) $pid --
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	: $((incr=incr+1))
 	_renice $((nice+incr)) -p -- $pid
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	: $((incr=incr+1))
 	_renice $((nice+incr)) -p $pid --
-	atf_check_equal $((nice+incr)) "$(ps -o nice= -p $pid)"
+	atf_check_nice_value $pid $((nice+incr))
 	kill $pid
 }
 
+atf_test_case renice_incr_noarg
+renice_incr_noarg_head() {
+	atf_set "descr" "Do not segfault if -n is given without an argument"
+}
+renice_incr_noarg_body() {
+	atf_check -o empty -e ignore -s exit:1 renice -n
+}
+
 atf_init_test_cases() {
 	atf_add_test_case renice_abs_pid
 	atf_add_test_case renice_rel_pid
 	atf_add_test_case renice_abs_pgid
 	atf_add_test_case renice_rel_pgid
 	atf_add_test_case renice_abs_user
 	atf_add_test_case renice_rel_user
 	atf_add_test_case renice_delim
+	atf_add_test_case renice_incr_noarg
 }