diff --git a/etc/mtree/BSD.tests.dist b/etc/mtree/BSD.tests.dist
--- a/etc/mtree/BSD.tests.dist
+++ b/etc/mtree/BSD.tests.dist
@@ -902,6 +902,8 @@
     usr.bin
         apply
         ..
+        asa
+        ..
         awk
             bugs-fixed
             ..
diff --git a/usr.bin/asa/Makefile b/usr.bin/asa/Makefile
--- a/usr.bin/asa/Makefile
+++ b/usr.bin/asa/Makefile
@@ -1,6 +1,7 @@
-#	$NetBSD: Makefile,v 1.2 1995/03/25 18:04:51 glass Exp $
-# $FreeBSD$
+.include <src.opts.mk>
 
 PROG=	asa
+HAS_TESTS=
+SUBDIR.${MK_TESTS}=	tests
 
 .include <bsd.prog.mk>
diff --git a/usr.bin/asa/tests/Makefile b/usr.bin/asa/tests/Makefile
new file mode 100644
--- /dev/null
+++ b/usr.bin/asa/tests/Makefile
@@ -0,0 +1,4 @@
+PACKAGE=	tests
+ATF_TESTS_SH=	asa_test
+
+.include <bsd.test.mk>
diff --git a/usr.bin/asa/tests/asa_test.sh b/usr.bin/asa/tests/asa_test.sh
new file mode 100644
--- /dev/null
+++ b/usr.bin/asa/tests/asa_test.sh
@@ -0,0 +1,99 @@
+#
+# Copyright (c) 2023 Klara, Inc.
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+
+a="The magic words are"
+b="Squeamish Ossifrage"
+
+atf_check_asa() {
+	atf_check -o file:"$2" asa "$1"
+	atf_check -o file:"$2" asa <"$1"
+	atf_check -o file:"$2" asa - <"$1"
+}
+
+atf_test_case space
+space_head() {
+	atf_set descr "First character on line is ' '"
+}
+space_body() {
+	printf " %s\n %s\n" "$a" "$b" >infile
+	printf "%s\n%s\n" "$a" "$b" >outfile
+	atf_check_asa infile outfile
+}
+
+atf_test_case zero
+zero_head() {
+	atf_set descr "First character on line is '0'"
+}
+zero_body() {
+	printf " %s\n0%s\n" "$a" "$b" >infile
+	printf "%s\n\n%s\n" "$a" "$b" >outfile
+	atf_check_asa infile outfile
+}
+
+atf_test_case one
+one_head() {
+	atf_set descr "First character on line is '1'"
+}
+one_body() {
+	printf " %s\n1%s\n" "$a" "$b" >infile
+	printf "%s\f%s\n" "$a" "$b" >outfile
+	atf_check_asa infile outfile
+}
+
+atf_test_case plus
+plus_head() {
+	atf_set descr "First character on line is '+'"
+}
+plus_body() {
+	printf " %s\n+%s\n" "$a" "$b" >infile
+	printf "%s\r%s\n" "$a" "$b" >outfile
+	atf_check_asa infile outfile
+}
+
+atf_test_case plus_top
+plus_top_head() {
+	atf_set descr "First character in input is '+'"
+}
+plus_top_body() {
+	printf "+%s\n+%s\n" "$a" "$b" >infile
+	printf "%s\r%s\n" "$a" "$b" >outfile
+	atf_check_asa infile outfile
+}
+
+atf_test_case stdout
+stdout_head() {
+	atf_set descr "Failure to write to stdout"
+}
+stdout_body() {
+	(
+		trap "" PIPE
+		echo " $a $b" | asa 2>stderr
+		echo $? >result
+	) | true
+	atf_check -o inline:"1\n" cat result
+	atf_check -o match:"stdout" cat stderr
+}
+
+atf_test_case dashdash
+dashdash_head() {
+	atf_set descr "Use -- to end options"
+}
+dashdash_body() {
+	echo " $a $b" >-infile
+	atf_check -s not-exit:0 -e match:"illegal option" asa -infile
+	atf_check -o inline:"$a $b\n" asa -- -infile
+}
+
+atf_init_test_cases()
+{
+	atf_add_test_case space
+	atf_add_test_case zero
+	atf_add_test_case one
+	atf_add_test_case plus
+	atf_add_test_case plus_top
+	atf_add_test_case stdout
+	atf_add_test_case dashdash
+}