Some snprintf testing in POSIX sh

#!/bin/sh

. /usr/share/bsdconfig/strings.subr || exit

N=1
EXIT=${SUCCESS:-0}
HR="--------------------"
VERBOSE=

hrprint() { printf "%s #%03u %s\n" "$HR" "$N" "$HR"; }
hr() { [ "$VERBOSE" ] && hrprint; }

xt()
{
    local testvalue="$1"
    shift 2 # testvalue ==
    hr
    f_snprintf result "$@"
    if [ "$result" = "$testvalue" ]; then
        [ "$VERBOSE" ] && echo f_snprintf "$@" == "$result"
    else
        [ "$VERBOSE" ] || hrprint
        echo f_snprintf "$@" == "$result [bad; expected $testvalue]"
        EXIT=${FAILURE:-1}
    fi
    N=$(( $N + 1 ))
}

: 001 ; xt "" == 0 "abc123"
: 002 ; xt "a" == 1 "abc123"
: 003 ; xt "ab" == 2 "abc123"
: 004 ; xt "abc" == 3 "abc123"
: 005 ; xt "abc1" == 4 "abc123"
: 006 ; xt "abc12" == 5 "abc123"
: 007 ; xt "abc123" == 6 "abc123"
: 008 ; xt "abc123" == 7 "abc123"
: 009 ; xt "" == 9  ""
: 010 ; xt "a" == 1 "abc123def456"
: 011 ; xt "ab" == 2 "abc123def456"
: 012 ; xt "abc" == 3 "abc123def456"
: 013 ; xt "abc1" == 4 "abc123def456"
: 014 ; xt "abc12" == 5 "abc123def456"
: 015 ; xt "abc123" == 6 "abc123def456"
: 016 ; xt "abc123d" == 7 "abc123def456"
: 017 ; xt "abc123de" == 8 "abc123def456"
: 018 ; xt "abc123def" == 9 "abc123def456"
: 019 ; xt "abc123def4" == 10 "abc123def456"
: 020 ; xt "abc123def45" == 11 "abc123def456"
: 021 ; xt "abc123def456" == 12 "abc123def456"
: 022 ; xt "abc123def456" == 13 "abc123def456"
: 023 ; xt "abc123def456" == 1025 "abc123def456"
: 024 ; xt "abc12" == 5 "abc123def456ghi789jkl0./"
: 025 ; xt "abc123d" == 7 "abc123def456ghi789jkl0./"
: 026 ; xt "abc123def" == 9 "abc123def456ghi789jkl0./"
: 027 ; xt "abc123def4" == 10 "abc123def456ghi789jkl0./"
: 028 ; xt "abc123def45" == 11 "abc123def456ghi789jkl0./"
: 029 ; xt "abc123def456" == 12 "abc123def456ghi789jkl0./"
: 030 ; xt "abc123def456g" == 13 "abc123def456ghi789jkl0./"
: 031 ; xt "abc123def456gh" == 14 "abc123def456ghi789jkl0./"
: 032 ; xt "abc123def456ghi" == 15 "abc123def456ghi789jkl0./"
: 033 ; xt "abc123def456ghi7" == 16 "abc123def456ghi789jkl0./"
: 034 ; xt "abc123def456ghi78" == 17 "abc123def456ghi789jkl0./"
: 035 ; xt "abc123def456ghi789" == 18 "abc123def456ghi789jkl0./"
: 036 ; xt "abc123def456ghi789j" == 19 "abc123def456ghi789jkl0./"
: 037 ; xt "abc123def456ghi789jk" == 20 "abc123def456ghi789jkl0./"
: 038 ; xt "abc123def456ghi789jkl" == 21 "abc123def456ghi789jkl0./"
: 039 ; xt "abc123def456ghi789jkl0" == 22 "abc123def456ghi789jkl0./"
: 040 ; xt "abc123def456ghi789jkl0." == 23 "abc123def456ghi789jkl0./"
: 041 ; xt "abc123def456ghi789jkl0./" == 24 "abc123def456ghi789jkl0./"
: 042 ; xt "abc123def456ghi789jkl0./" == 25 "abc123def456ghi789jkl0./"

exit $EXIT