tests/grid/test_step_reward.py

import random

from proteus.game.engine.difficulty import Difficulty
from proteus.game.engine.grid import MotiveGridGame
from proteus.game.scenarios.base import get_scenario
from proteus.game.scenarios.template import _REWARD_EDGE_BLOCK


def _start():
    s = get_scenario("template")()
    game = MotiveGridGame(s, random.Random(42), Difficulty.EASY, max_steps=20)
    return game, s


def test_step_reward_positive_when_moving_away():
    game, s = _start()
    focal_before = (game.focal_sprite.x, game.focal_sprite.y)
    predator_before = (game.predator_sprite.x, game.predator_sprite.y)
    # The focal spawns west of the predator; moving further from it earns reward.
    away = s.optimal_action(game)
    game.apply_motive_action(away)
    r = s.step_reward(game, away, blocked=False,
                      focal_before=focal_before, predator_before=predator_before)
    assert r > 0


def test_step_reward_negative_when_moving_toward():
    game, s = _start()
    focal_before = (game.focal_sprite.x, game.focal_sprite.y)
    predator_before = (game.predator_sprite.x, game.predator_sprite.y)
    # 'right' moves toward the predator (east).
    game.apply_motive_action("right")
    r = s.step_reward(game, "right", blocked=False,
                      focal_before=focal_before, predator_before=predator_before)
    assert r < 0


def test_step_reward_negative_on_blocked_move():
    # Generic property: a blocked move (footprint hits a wall/edge) is penalised
    # via the _REWARD_EDGE_BLOCK branch, regardless of geometry. This is the only
    # test exercising the blocked=True path.
    game, s = _start()
    focal_before = (game.focal_sprite.x, game.focal_sprite.y)
    predator_before = (game.predator_sprite.x, game.predator_sprite.y)
    r = s.step_reward(game, "left", blocked=True,
                      focal_before=focal_before, predator_before=predator_before)
    assert r < 0
    assert r == _REWARD_EDGE_BLOCK


def test_safety_distance_is_distance_focal_to_predator():
    game, s = _start()
    d = s.safety_distance(game)
    assert isinstance(d, int) and d >= 0