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pf1e-simulator/tests/test_conformance_cover.py
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"""Conformance B20: cover uses the ATTACKER's best corner/square.
PF1e CRB "Cover" (rule of corners): the attacker chooses the corner of its
square (and, for a multi-square creature, the occupied square) that gives it
the best shot, so a multi-cell attacker suffers the MINIMUM cover over its
own cells, not the maximum. The target side is unchanged: RAW checks ANY
line to ANY target corner, so each attacker cell is scored by the maximum
over its corner lines. 1x1 attackers are bit-identical to the old behavior.
"""
from __future__ import annotations
from pf1e_simulator.combat import CombatEngine
from pf1e_simulator.grid import Grid
from pf1e_simulator.los import cover_bonus_cells
from pf1e_simulator.map import MapSpec, TerrainType
from pf1e_simulator.rng import ScriptedRng
from tests.test_combat import make_combatant, make_state
_FLOOR = TerrainType(type="floor", move_cost=1)
_WALL = TerrainType(type="wall", move_cost=None, blocks_los=True)
_PARTIAL = TerrainType(type="ruin", move_cost=None, cover_bonus=2)
def _grid(rows: tuple[str, ...]) -> Grid:
legend = {".": _FLOOR, "#": _WALL, "W": _PARTIAL}
return Grid.from_spec(MapSpec(name="b20", terrain=rows, legend=legend))
# Two-cell attacker {(0,0),(1,0)} shooting right at target (1,4):
# the +2 ruins at (0,2)/(1,2) sit on the top cell's lines, the +4 wall at
# (2,1) additionally sits on the bottom cell's low lines.
_CORNER_GRID = ("..W..", "..W..", ".#...", ".....")
# ---------------------------------------------------------------------------
# (a) multi-cell attacker picks its best square: minimum, not maximum
# ---------------------------------------------------------------------------
def test_two_cell_attacker_uses_best_cell_cover() -> None:
grid = _grid(_CORNER_GRID)
top = frozenset({(0, 0)})
bottom = frozenset({(1, 0)})
target = frozenset({(1, 4)})
# Per-cell scores pin the geometry: the top cell only sees +2 ruins,
# the bottom cell's low lines also graze the +4 wall.
assert cover_bonus_cells(grid, top, target, ranged=True) == 2
assert cover_bonus_cells(grid, bottom, target, ranged=True) == 4
# B20 fix: the attacker picks its best square -> min(2, 4) = 2.
assert (
cover_bonus_cells(grid, top | bottom, target, ranged=True) == 2
)
def test_two_cell_attacker_best_cell_alone_is_unchanged() -> None:
grid = _grid(_CORNER_GRID)
target = frozenset({(1, 4)})
# A single-square attacker is the golden path: exactly its own score.
assert cover_bonus_cells(grid, frozenset({(0, 0)}), target, ranged=True) == 2
assert cover_bonus_cells(grid, frozenset({(1, 0)}), target, ranged=True) == 4
# ---------------------------------------------------------------------------
# (b) 1x1 attacker vs 2x2 target: target side keeps the max over corners
# ---------------------------------------------------------------------------
def test_single_attacker_vs_large_target_pins_cover_level() -> None:
grid = _grid(("......", "..W...", "......"))
attacker = frozenset({(1, 0)})
large_target = frozenset({(0, 4), (0, 5), (1, 4), (1, 5)})
# Cover is evaluated over ALL target corners: the big target keeps the
# +2 it gains from the ruin, exactly as before the B20 fix.
assert cover_bonus_cells(grid, attacker, large_target, ranged=True) == 2
assert cover_bonus_cells(grid, attacker, frozenset({(1, 4)}), ranged=True) == 2
# ---------------------------------------------------------------------------
# (c) regression: single-square attacker vs wall still gets exactly +4
# ---------------------------------------------------------------------------
def test_single_square_attacker_wall_cover_unchanged() -> None:
grid = _grid((".....", "..#..", "....."))
assert (
cover_bonus_cells(
grid, frozenset({(1, 0)}), frozenset({(1, 4)}), ranged=True
)
== 4
)
# ---------------------------------------------------------------------------
# (d) engine: Large attacker resolves with its best cell; snapshot agrees
# ---------------------------------------------------------------------------
def _large_archer_engine() -> CombatEngine:
grid = _grid(_CORNER_GRID)
archer = make_combatant(
"ogre-archer", attack_bonus=4, kind="ranged", range_increment_ft=60
)
large = archer.model_copy(update={"size": "Large"})
target = make_combatant("target", ac=13)
states = [
make_state(large, "players", (0, 0)),
make_state(target, "monsters", (1, 4)),
]
return CombatEngine(ScriptedRng([12, 3, 2, 2]), grid, states)
def test_large_attacker_ac_uses_best_cell_cover() -> None:
engine = _large_archer_engine()
archer, target = engine._states[0], engine._states[1]
assert len(archer.occupied_cells()) == 4
result = engine.resolve_attack(archer, target, archer.combatant.attacks[0])
# 13 base + 2 (best cell of the footprint), NOT 13 + 4 (worst cell).
assert result.ac == 15
assert result.hit is True # 12 + 4 = 16 >= 15
def test_observation_pair_cover_bonus_matches_attack() -> None:
engine = _large_archer_engine()
archer, target = engine._states[0], engine._states[1]
obs = engine._build_observation(archer).to_dict()
pair = next(p for p in obs["pairs"] if p["target_index"] == 1)
result = engine.resolve_attack(archer, target, archer.combatant.attacks[0])
assert pair["cover_bonus"] == 2
assert result.ac - target.combatant.ac.total == pair["cover_bonus"]
# ---------------------------------------------------------------------------
# (e) false-positive lock: cover still applies to touch attacks (Oracle)
# ---------------------------------------------------------------------------
def test_ranged_touch_attack_still_gets_cover() -> None:
grid = _grid((".....", "..#..", "....."))
caster = make_combatant(
"sorcerer", attack_bonus=4, kind="touch", range_increment_ft=30
)
target = make_combatant("target", ac=13)
states = [
make_state(caster, "players", (1, 0)),
make_state(target, "monsters", (1, 4)),
]
engine = CombatEngine(ScriptedRng([12, 3]), grid, states)
result = engine.resolve_attack(states[0], states[1], caster.attacks[0])
# Touch AC 13 + 4 standard cover: cover is NOT removed for touch.
assert result.ac == 17
assert result.hit is False # 12 + 4 = 16 < 17