{"abstract":"A black pawn on d4 cannot capture en passant on e3.","category":"Chess move legality","checks":8,"contract":"Input: {\"board\", \"move\": [from, to], \"ep\": target square or null}. Return true when the move is a legal en passant capture: a pawn on its fifth rank moves diagonally forward onto the ep square, an enemy pawn stands beside it on the origin rank, and after removing both pawns from their squares and placing the capturer, no enemy rook, bishop or queen attacks the mover's king along an open line.","evaluation_group":"w2-chess_move_legality-en-passant-legality","failed_approach":"Swapping the indices breaks both colours.","family":"w2-chess_move_legality-en-passant-legality-fifth-rank-requirement","id":"FA-82421","implementations":{"attempt":{"sha256":"dc9bab643ca459b41baae7dc81bc7f525fe17028515f49f99d58df2801b3f8ba","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    b=dict(x['board']); fr,to=x['move']; p=b.get(fr)\n    if p not in ('P','p') or to!=x['ep']: return False\n    white=p=='P'\n    d=1 if white else -1\n    f0,r0=ord(fr[0])-97,int(fr[1])-1\n    f1,r1=ord(to[0])-97,int(to[1])-1\n    if r1-r0!=d or abs(f1-f0)!=1: return False\n    if r0!=(3 if white else 4): return False\n    victim=to[0]+fr[1]\n    if b.get(victim)!=('p' if white else 'P'): return False\n    del b[fr]; del b[victim]; b[to]=p\n    ks=[s for s,v in b.items() if v==('K' if white else 'k')][0]\n    kf,kr=ord(ks[0])-97,int(ks[1])-1\n    for df,dr in ((1,0),(-1,0),(0,1),(0,-1),(1,1),(1,-1),(-1,1),(-1,-1)):\n        cf,cr=kf+df,kr+dr\n        while 0<=cf<8 and 0<=cr<8:\n            v=b.get(chr(97+cf)+str(cr+1))\n            if v:\n                if v.isupper()!=white and v.lower() in (('r','q') if df==0 or dr==0 else ('b','q')): return False\n                break\n            cf+=df; cr+=dr\n    return True\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[('plain ep',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd6', 'move': ['e5', 'd6']},\n   True),\n  ('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('rank pin both pawns',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False),\n  ('rank pin black side',\n   {'board': {'a4': 'Q', 'd4': 'p', 'e1': 'K', 'e4': 'P', 'h4': 'k'},\n    'ep': 'e3',\n    'move': ['d4', 'e3']},\n   False),\n  ('no ep square',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': None, 'move': ['e5', 'd6']},\n   False),\n  ('wrong target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p'},\n    'ep': 'd6',\n    'move': ['e5', 'f6']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('same file ep target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd3', 'move': ['e5', 'd6']},\n   False)],\n [('plain ep',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd6', 'move': ['e5', 'd6']},\n   True),\n  ('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('bishop diagonal after ep',\n   {'board': {'c3': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p', 'f6': 'n', 'h8': 'b'},\n    'ep': 'f6',\n    'move': ['e5', 'f6']},\n   True),\n  ('wrong target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p'},\n    'ep': 'd6',\n    'move': ['e5', 'f6']},\n   False),\n  ('wrong rank for white',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'd5', 'move': ['e4', 'd5']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('same file ep target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd3', 'move': ['e5', 'd6']},\n   False),\n  ('rook on file of ep square',\n   {'board': {'a1': 'K', 'd1': 'r', 'd5': 'p', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False)],\n [('plain ep',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd6', 'move': ['e5', 'd6']},\n   True),\n  ('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('bishop diagonal after ep',\n   {'board': {'c3': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p', 'f6': 'n', 'h8': 'b'},\n    'ep': 'f6',\n    'move': ['e5', 'f6']},\n   True),\n  ('wrong rank for white',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'd5', 'move': ['e4', 'd5']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('file rook behind pawn',\n   {'board': {'d1': 'K', 'd5': 'p', 'd8': 'r', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('pin by own rook harmless',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'R'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('bishop on the rank',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'b'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True)],\n [('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('rank pin both pawns',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False),\n  ('wrong rank for white',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'd5', 'move': ['e4', 'd5']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('file rook behind pawn',\n   {'board': {'d1': 'K', 'd5': 'p', 'd8': 'r', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('pin by own rook harmless',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'R'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('bishop on the rank',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'b'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('rook on the diagonal',\n   {'board': {'c3': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'g7': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True)],\n [('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('rank pin both pawns',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False),\n  ('rank pin black side',\n   {'board': {'a4': 'Q', 'd4': 'p', 'e1': 'K', 'e4': 'P', 'h4': 'k'},\n    'ep': 'e3',\n    'move': ['d4', 'e3']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('file rook behind pawn',\n   {'board': {'d1': 'K', 'd5': 'p', 'd8': 'r', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('pin by own rook harmless',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'R'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('bishop on the rank',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'b'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('rook on the diagonal',\n   {'board': {'c3': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'g7': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True)]]\nfor label, args, expected in fixtures[N-1]:\n    try:\n        actual = solve(args)\n    except Exception as exc:\n        actual = 'error:' + type(exc).__name__\n    check(label, actual, expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"4c5ae6a8d653ccb17a93137b1d8b77d942c2c8730fa36a12354932df737b538f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    b=dict(x['board']); fr,to=x['move']; p=b.get(fr)\n    if p not in ('P','p') or to!=x['ep']: return False\n    white=p=='P'\n    d=1 if white else -1\n    f0,r0=ord(fr[0])-97,int(fr[1])-1\n    f1,r1=ord(to[0])-97,int(to[1])-1\n    if r1-r0!=d or abs(f1-f0)!=1: return False\n    if r0!=4: return False\n    victim=to[0]+fr[1]\n    if b.get(victim)!=('p' if white else 'P'): return False\n    del b[fr]; del b[victim]; b[to]=p\n    ks=[s for s,v in b.items() if v==('K' if white else 'k')][0]\n    kf,kr=ord(ks[0])-97,int(ks[1])-1\n    for df,dr in ((1,0),(-1,0),(0,1),(0,-1),(1,1),(1,-1),(-1,1),(-1,-1)):\n        cf,cr=kf+df,kr+dr\n        while 0<=cf<8 and 0<=cr<8:\n            v=b.get(chr(97+cf)+str(cr+1))\n            if v:\n                if v.isupper()!=white and v.lower() in (('r','q') if df==0 or dr==0 else ('b','q')): return False\n                break\n            cf+=df; cr+=dr\n    return True\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[('plain ep',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd6', 'move': ['e5', 'd6']},\n   True),\n  ('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('rank pin both pawns',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False),\n  ('rank pin black side',\n   {'board': {'a4': 'Q', 'd4': 'p', 'e1': 'K', 'e4': 'P', 'h4': 'k'},\n    'ep': 'e3',\n    'move': ['d4', 'e3']},\n   False),\n  ('no ep square',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': None, 'move': ['e5', 'd6']},\n   False),\n  ('wrong target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p'},\n    'ep': 'd6',\n    'move': ['e5', 'f6']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('same file ep target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd3', 'move': ['e5', 'd6']},\n   False)],\n [('plain ep',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd6', 'move': ['e5', 'd6']},\n   True),\n  ('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('bishop diagonal after ep',\n   {'board': {'c3': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p', 'f6': 'n', 'h8': 'b'},\n    'ep': 'f6',\n    'move': ['e5', 'f6']},\n   True),\n  ('wrong target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p'},\n    'ep': 'd6',\n    'move': ['e5', 'f6']},\n   False),\n  ('wrong rank for white',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'd5', 'move': ['e4', 'd5']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('same file ep target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd3', 'move': ['e5', 'd6']},\n   False),\n  ('rook on file of ep square',\n   {'board': {'a1': 'K', 'd1': 'r', 'd5': 'p', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False)],\n [('plain ep',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd6', 'move': ['e5', 'd6']},\n   True),\n  ('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('bishop diagonal after ep',\n   {'board': {'c3': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p', 'f6': 'n', 'h8': 'b'},\n    'ep': 'f6',\n    'move': ['e5', 'f6']},\n   True),\n  ('wrong rank for white',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'd5', 'move': ['e4', 'd5']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('file rook behind pawn',\n   {'board': {'d1': 'K', 'd5': 'p', 'd8': 'r', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('pin by own rook harmless',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'R'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('bishop on the rank',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'b'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True)],\n [('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('rank pin both pawns',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False),\n  ('wrong rank for white',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'd5', 'move': ['e4', 'd5']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('file rook behind pawn',\n   {'board': {'d1': 'K', 'd5': 'p', 'd8': 'r', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('pin by own rook harmless',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'R'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('bishop on the rank',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'b'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('rook on the diagonal',\n   {'board': {'c3': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'g7': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True)],\n [('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('rank pin both pawns',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False),\n  ('rank pin black side',\n   {'board': {'a4': 'Q', 'd4': 'p', 'e1': 'K', 'e4': 'P', 'h4': 'k'},\n    'ep': 'e3',\n    'move': ['d4', 'e3']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('file rook behind pawn',\n   {'board': {'d1': 'K', 'd5': 'p', 'd8': 'r', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('pin by own rook harmless',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'R'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('bishop on the rank',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'b'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('rook on the diagonal',\n   {'board': {'c3': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'g7': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True)]]\nfor label, args, expected in fixtures[N-1]:\n    try:\n        actual = solve(args)\n    except Exception as exc:\n        actual = 'error:' + type(exc).__name__\n    check(label, actual, expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"fixed":{"sha256":"ae8cd98d949bb798012f76f8562082afd42c7f71c01220abad0c3216bc3a9925","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    b=dict(x['board']); fr,to=x['move']; p=b.get(fr)\n    if p not in ('P','p') or to!=x['ep']: return False\n    white=p=='P'\n    d=1 if white else -1\n    f0,r0=ord(fr[0])-97,int(fr[1])-1\n    f1,r1=ord(to[0])-97,int(to[1])-1\n    if r1-r0!=d or abs(f1-f0)!=1: return False\n    if r0!=(4 if white else 3): return False\n    victim=to[0]+fr[1]\n    if b.get(victim)!=('p' if white else 'P'): return False\n    del b[fr]; del b[victim]; b[to]=p\n    ks=[s for s,v in b.items() if v==('K' if white else 'k')][0]\n    kf,kr=ord(ks[0])-97,int(ks[1])-1\n    for df,dr in ((1,0),(-1,0),(0,1),(0,-1),(1,1),(1,-1),(-1,1),(-1,-1)):\n        cf,cr=kf+df,kr+dr\n        while 0<=cf<8 and 0<=cr<8:\n            v=b.get(chr(97+cf)+str(cr+1))\n            if v:\n                if v.isupper()!=white and v.lower() in (('r','q') if df==0 or dr==0 else ('b','q')): return False\n                break\n            cf+=df; cr+=dr\n    return True\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[('plain ep',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd6', 'move': ['e5', 'd6']},\n   True),\n  ('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('rank pin both pawns',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False),\n  ('rank pin black side',\n   {'board': {'a4': 'Q', 'd4': 'p', 'e1': 'K', 'e4': 'P', 'h4': 'k'},\n    'ep': 'e3',\n    'move': ['d4', 'e3']},\n   False),\n  ('no ep square',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': None, 'move': ['e5', 'd6']},\n   False),\n  ('wrong target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p'},\n    'ep': 'd6',\n    'move': ['e5', 'f6']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('same file ep target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd3', 'move': ['e5', 'd6']},\n   False)],\n [('plain ep',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd6', 'move': ['e5', 'd6']},\n   True),\n  ('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('bishop diagonal after ep',\n   {'board': {'c3': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p', 'f6': 'n', 'h8': 'b'},\n    'ep': 'f6',\n    'move': ['e5', 'f6']},\n   True),\n  ('wrong target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p'},\n    'ep': 'd6',\n    'move': ['e5', 'f6']},\n   False),\n  ('wrong rank for white',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'd5', 'move': ['e4', 'd5']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('same file ep target',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd3', 'move': ['e5', 'd6']},\n   False),\n  ('rook on file of ep square',\n   {'board': {'a1': 'K', 'd1': 'r', 'd5': 'p', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False)],\n [('plain ep',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'd6', 'move': ['e5', 'd6']},\n   True),\n  ('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('bishop diagonal after ep',\n   {'board': {'c3': 'K', 'e5': 'P', 'e8': 'k', 'f5': 'p', 'f6': 'n', 'h8': 'b'},\n    'ep': 'f6',\n    'move': ['e5', 'f6']},\n   True),\n  ('wrong rank for white',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'd5', 'move': ['e4', 'd5']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('file rook behind pawn',\n   {'board': {'d1': 'K', 'd5': 'p', 'd8': 'r', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('pin by own rook harmless',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'R'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('bishop on the rank',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'b'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True)],\n [('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('rank pin both pawns',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False),\n  ('wrong rank for white',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'd5', 'move': ['e4', 'd5']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('file rook behind pawn',\n   {'board': {'d1': 'K', 'd5': 'p', 'd8': 'r', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('pin by own rook harmless',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'R'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('bishop on the rank',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'b'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('rook on the diagonal',\n   {'board': {'c3': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'g7': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True)],\n [('black ep',\n   {'board': {'d4': 'p', 'e1': 'K', 'e4': 'P', 'e8': 'k'}, 'ep': 'e3', 'move': ['d4', 'e3']},\n   True),\n  ('rank pin both pawns',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   False),\n  ('rank pin black side',\n   {'board': {'a4': 'Q', 'd4': 'p', 'e1': 'K', 'e4': 'P', 'h4': 'k'},\n    'ep': 'e3',\n    'move': ['d4', 'e3']},\n   False),\n  ('black wrong rank',\n   {'board': {'d5': 'p', 'e1': 'K', 'e5': 'P', 'e8': 'k'}, 'ep': 'e4', 'move': ['d5', 'e4']},\n   False),\n  ('file rook behind pawn',\n   {'board': {'d1': 'K', 'd5': 'p', 'd8': 'r', 'e5': 'P', 'e8': 'k'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('pin by own rook harmless',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'R'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('bishop on the rank',\n   {'board': {'a5': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'h5': 'b'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True),\n  ('rook on the diagonal',\n   {'board': {'c3': 'K', 'd5': 'p', 'e5': 'P', 'e8': 'k', 'g7': 'r'},\n    'ep': 'd6',\n    'move': ['e5', 'd6']},\n   True)]]\nfor label, args, expected in fixtures[N-1]:\n    try:\n        actual = solve(args)\n    except Exception as exc:\n        actual = 'error:' + type(exc).__name__\n    check(label, actual, expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"A deterministic toy model with an explicitly stated contract; boards are {square: piece} with white upper-case and black lower-case pieces; no claim of full FIDE Laws conformance. 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.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"w2-chess_move_legality-en-passant-legality-fifth-rank-requirement","generated_at":"2026-09-29T14:50:12.053920+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Move validators gate every move in engines, servers and arbiters; accepting an illegal move or rejecting a legal one corrupts the game record.","repair":"White captures from rank index 4, black from rank index 3.","root_cause":"The capturer rank is hard-coded to white's fifth rank for both colours.","sha256":"e70f5a0d2af0bd0acc6302433bdcee583f9c423e757c91d5dfe55aeec29001c1","title":"Black en passant rejected on its fifth rank · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":41.922,"exit_code":1,"observations":[{"actual":false,"check":"plain ep","expected":true,"passed":false},{"actual":false,"check":"black ep","expected":true,"passed":false},{"actual":false,"check":"rank pin both pawns","expected":false,"passed":true},{"actual":false,"check":"rank pin black side","expected":false,"passed":true},{"actual":false,"check":"no ep square","expected":false,"passed":true},{"actual":false,"check":"wrong target","expected":false,"passed":true},{"actual":true,"check":"black wrong rank","expected":false,"passed":false},{"actual":false,"check":"same file ep target","expected":false,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"plain ep\", \"actual\": false, \"expected\": true, \"passed\": false}, {\"check\": \"black ep\", \"actual\": false, \"expected\": true, \"passed\": false}, {\"check\": \"rank pin both pawns\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"rank pin black side\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"no ep square\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"wrong target\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"black wrong rank\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"same file ep target\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":42.894,"exit_code":1,"observations":[{"actual":true,"check":"plain ep","expected":true,"passed":true},{"actual":false,"check":"black ep","expected":true,"passed":false},{"actual":false,"check":"rank pin both pawns","expected":false,"passed":true},{"actual":false,"check":"rank pin black side","expected":false,"passed":true},{"actual":false,"check":"no ep square","expected":false,"passed":true},{"actual":false,"check":"wrong target","expected":false,"passed":true},{"actual":true,"check":"black wrong rank","expected":false,"passed":false},{"actual":false,"check":"same file ep target","expected":false,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"plain ep\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"black ep\", \"actual\": false, \"expected\": true, \"passed\": false}, {\"check\": \"rank pin both pawns\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"rank pin black side\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"no ep square\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"wrong target\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"black wrong rank\", \"actual\": true, \"expected\": false, \"passed\": false}, {\"check\": \"same file ep target\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":42.29,"exit_code":0,"observations":[{"actual":true,"check":"plain ep","expected":true,"passed":true},{"actual":true,"check":"black ep","expected":true,"passed":true},{"actual":false,"check":"rank pin both pawns","expected":false,"passed":true},{"actual":false,"check":"rank pin black side","expected":false,"passed":true},{"actual":false,"check":"no ep square","expected":false,"passed":true},{"actual":false,"check":"wrong target","expected":false,"passed":true},{"actual":false,"check":"black wrong rank","expected":false,"passed":true},{"actual":false,"check":"same file ep target","expected":false,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"plain ep\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"black ep\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"rank pin both pawns\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"rank pin black side\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"no ep square\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"wrong target\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"black wrong rank\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"same file ep target\", \"actual\": false, \"expected\": false, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}