FA-3351 / Encodings / Open access

ROT13 rotates non-ASCII letters · case 01

ROT13 rotates non-ASCII letters.

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: Apply ROT13 only to ASCII Latin letters, retaining case and punctuation.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Apply ROT13 only to ASCII Latin letters, retaining case and punctuation.

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

Case contract

Apply ROT13 only to ASCII Latin letters, retaining case and punctuation.

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 ''.join(chr((ord(c)-97+13)%26+97) if c.isalpha() else c for c in x)
    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('AbZ'), 'NoM')
check('boundary 2', solve('é'), 'é')
check('boundary 3', solve('Hello!'), 'Uryyb!')
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	`hog`	`NoM`	Failed
boundary 2	`t`	`é`	Failed
boundary 3	`oryyb!`	`Uryyb!`	Failed
boundary 4			Passed

SHA-256 / a6f1aff8075d4539c86345de85e015ee880e66e2b2caf6971b7e289feb99dfdd

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 ''.join(chr((ord(c.lower())-97+13)%26+97) if c.isalpha() else c for c in x)
    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('AbZ'), 'NoM')
check('boundary 2', solve('é'), 'é')
check('boundary 3', solve('Hello!'), 'Uryyb!')
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	`nom`	`NoM`	Failed
boundary 2	`t`	`é`	Failed
boundary 3	`uryyb!`	`Uryyb!`	Failed
boundary 4			Passed

SHA-256 / 9521a39916bb32db592cb433f7f4f6e9898c26a525f68f7176200a5a93ecfd93

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 codecs.encode(x,'rot_13')
    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('AbZ'), 'NoM')
check('boundary 2', solve('é'), 'é')
check('boundary 3', solve('Hello!'), 'Uryyb!')
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	`NoM`	`NoM`	Passed
boundary 2	`é`	`é`	Passed
boundary 3	`Uryyb!`	`Uryyb!`	Passed
boundary 4			Passed

SHA-256 / 6685b079da2f8642a30179df4cf73c5f3bc7db97f627a384f7f04c17fd2c80f0

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 2026-09-29T14:37:24.552829+00:00.

Case digest / 114a4b2df4bd592d3da811e0fa4ee45e4b4266666f20c794820158b1de9c3890