slsm: t: add test for /dev/fd pipe support

security/slsm/t/slsm-tests.sh

@@ -458,4 +458,9 @@ test_expect_success 'example mpv setup' "
     test_must_fail $PERL -e 'system(\"/usr/bin/head /tmp/slsm/home/user/private\") == 0 or exit 1'
 "
 
+test_expect_success '/dev/fd/ pipe support' '
+    test_when_finished cleanup && setup &&
+    bash -c "while read line; do :; done < <(echo hi)"
+'
+
 test_done