diff --git a/usr.bin/uniq/tests/uniq_test.sh b/usr.bin/uniq/tests/uniq_test.sh
index 804e82ce7766..9d37245dee4e 100755
--- a/usr.bin/uniq/tests/uniq_test.sh
+++ b/usr.bin/uniq/tests/uniq_test.sh
@@ -1,193 +1,195 @@
 #
 # Copyright (c) 2024 Klara, Inc.
 #
 # SPDX-License-Identifier: BSD-2-Clause
 #
 
 atf_check_uniq() {
 	atf_check uniq "$@" input actual
 	atf_check diff -u actual expected
 	atf_check uniq "$@" - actual <input
 	atf_check diff -u actual expected
 	atf_check -o file:expected uniq "$@" input
 	atf_check -o file:expected uniq "$@" <input
 	atf_check -o file:expected uniq "$@" - <input
 }
 
 atf_test_case basic
 basic_head() {
 	atf_set descr "basic test without options"
 }
 basic_body() {
 	printf "a\na\nb\nb\na\na\n" >input
 	printf "a\nb\na\n" >expected
 	atf_check_uniq
 }
 
 atf_test_case count
 count_head() {
 	atf_set descr "basic test showing counts"
 }
 count_body() {
 	printf "a\na\nb\nb\nb\na\na\na\na\n" >input
 	printf "   2 a\n   3 b\n   4 a\n" >expected
 	atf_check_uniq -c
 	atf_check_uniq --count
 }
 
 atf_test_case repeated
 repeated_head() {
 	atf_set descr "print repeated lines only"
 }
 repeated_body() {
 	printf "a\na\nb\na\na\n" >input
 	printf "a\na\n" >expected
 	atf_check_uniq -d
 	atf_check_uniq --repeated
 }
 
 atf_test_case count_repeated
 count_repeated_head() {
 	atf_set descr "count and print repeated lines only"
 }
 count_repeated_body() {
 	printf "a\na\nb\nb\na\n" >input
 	printf "   2 a\n   2 b\n" >expected
 	atf_check_uniq --count --repeated
 }
 
 atf_test_case all_repeated
 all_repeated_head() {
 	atf_set descr "print every instance of repeated lines"
 }
 all_repeated_body() {
 	printf "a\na\nb\na\na\n" >input
 	printf "a\na\na\na\n" >expected
 	atf_check_uniq -D
 	atf_check_uniq --all-repeated
 }
 
 atf_test_case skip_fields
 skip_fields_head() {
 	atf_set descr "skip fields"
 }
 skip_fields_body() {
 	printf "1 a\n2 a\n3 b\n4 b\n5 a\n6 a\n" >input
 	printf "1 a\n3 b\n5 a\n" >expected
 	atf_check_uniq -1
 	atf_check_uniq -f 1
 	atf_check_uniq --skip-fields 1
 }
 
 atf_test_case skip_fields_tab
 skip_fields_tab_head() {
 	atf_set descr "skip fields (with tabs)"
 }
 skip_fields_tab_body() {
 	printf "1\ta\n2\ta\n3\tb\n4\tb\n5\ta\n6\ta\n" >input
 	printf "1\ta\n3\tb\n5\ta\n" >expected
 	atf_check_uniq -1
 	atf_check_uniq -f 1
 	atf_check_uniq --skip-fields 1
 }
 
 atf_test_case ignore_case
 ignore_case_head() {
 	atf_set descr "ignore case"
 }
 ignore_case_body() {
 	printf "a\nA\nb\nB\na\nA\n" >input
 	printf "a\nb\na\n" >expected
 	atf_check_uniq -i
 	atf_check_uniq --ignore-case
 }
 
 atf_test_case skip_chars
 skip_chars_head() {
 	atf_set descr "skip chars"
 }
 skip_chars_body() {
 	printf "1 a\n2 a\n3 b\n4 b\n5 a\n6 a\n" >input
 	printf "1 a\n3 b\n5 a\n" >expected
 	atf_check_uniq +2
 	atf_check_uniq -s 2
 	atf_check_uniq --skip-chars 2
 }
 
 atf_test_case unique
 unique_head() {
 	atf_set descr "print non-repeated lines only"
 }
 unique_body() {
 	printf "a\na\nb\na\na\n" >input
 	printf "b\n" >expected
 	atf_check_uniq -u
 	atf_check_uniq --unique
 }
 
 atf_test_case count_unique
 count_unique_head() {
 	atf_set descr "print non-repeated lines with count"
 }
 count_unique_body() {
 	printf "a\na\nb\n" >input
 	printf "   1 b\n" >expected
 	atf_check_uniq --unique --count
 	atf_check_uniq --count --unique
 }
 
 atf_test_case interactive
 interactive_head() {
 	atf_set descr "test interactive use"
 }
 interactive_body() {
 	sh -c 'yes | stdbuf -oL uniq >actual' &
 	pid=$!
 	sleep 1
 	kill $!
 	atf_check -o inline:"y\n" cat actual
 }
 
 atf_test_case interactive_repeated
 interactive_repeated_head() {
 	atf_set descr "test interactive use with -d"
 }
 interactive_repeated_body() {
 	sh -c 'yes | stdbuf -oL uniq -d >actual' &
 	pid=$!
 	sleep 1
 	kill $!
 	atf_check -o inline:"y\n" cat actual
 }
 
 atf_test_case stdout
 stdout_head() {
 	atf_set descr "error writing to stdout"
 }
 stdout_body() {
 	(
 		trap "" PIPE
+		# Give true(1) some time to exit.
+		sleep 1
 		echo a | uniq 2>stderr
 		echo $? >result
 	) | true
 	atf_check -o inline:"1\n" cat result
 	atf_check -o match:"stdout" cat stderr
 }
 
 atf_init_test_cases()
 {
 	atf_add_test_case basic
 	atf_add_test_case count
 	atf_add_test_case repeated
 	atf_add_test_case count_repeated
 	atf_add_test_case all_repeated
 	atf_add_test_case skip_fields
 	atf_add_test_case skip_fields_tab
 	atf_add_test_case ignore_case
 	atf_add_test_case skip_chars
 	atf_add_test_case unique
 	atf_add_test_case count_unique
 	atf_add_test_case interactive
 	atf_add_test_case interactive_repeated
 	atf_add_test_case stdout
 }