FA-3046 / Text processing / Open access

Odd center padding goes to the wrong side · case 01

Odd center padding goes to the wrong side.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The implementation applies an operation whose text or grammar semantics violate this contract: Center a string to width six using periods and Python centering allocation.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Center a string to width six using periods and Python centering allocation.

Unsuccessful approach: The attempted repair handles the primary example but still violates a separate boundary of the same contract.

Case contract

Center a string to width six using periods and Python centering allocation.

Why this case matters

A local executable model for consumers of structured text; oracle values are authored literals, not outputs copied from the repaired implementation.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return x.ljust(6,'.')
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve('abc'), '.abc..')
check('boundary 2', solve('ab'), '..ab..')
check('boundary 3', solve('abcdefg'), 'abcdefg')
check('boundary 4', solve(''), '......')
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
boundary 1	`abc...`	`.abc..`	Failed
boundary 2	`ab....`	`..ab..`	Failed
boundary 3	`abcdefg`	`abcdefg`	Passed
boundary 4	`......`	`......`	Passed

SHA-256 / 964f5802e8888209fc20837b3332a8bb15432e17210575c59bab771790000b47

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return '.'*((6-len(x)+1)//2)+x+'.'*max(0,(6-len(x))//2)
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve('abc'), '.abc..')
check('boundary 2', solve('ab'), '..ab..')
check('boundary 3', solve('abcdefg'), 'abcdefg')
check('boundary 4', solve(''), '......')
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
boundary 1	`..abc.`	`.abc..`	Failed
boundary 2	`..ab..`	`..ab..`	Passed
boundary 3	`abcdefg`	`abcdefg`	Passed
boundary 4	`......`	`......`	Passed

SHA-256 / a45874f81cb4caa010816659b635ca4c9314dbf234d6922b85f9e1f355f73dc1

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return x.center(6,'.')
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve('abc'), '.abc..')
check('boundary 2', solve('ab'), '..ab..')
check('boundary 3', solve('abcdefg'), 'abcdefg')
check('boundary 4', solve(''), '......')
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
boundary 1	`.abc..`	`.abc..`	Passed
boundary 2	`..ab..`	`..ab..`	Passed
boundary 3	`abcdefg`	`abcdefg`	Passed
boundary 4	`......`	`......`	Passed

SHA-256 / c1589c49936bb7c17f8f17ad2cdd7291f64d50881341bac0a0ae092e00a15330

Verification & scope

This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:37:20.759320+00:00.

Case digest / bb2f2d373d550e4e8a05f03473004922c89760f4ba9ab3e8296eb49715535248