src/snake_game/food.py

@@ -0,0 +1,49 @@
+"""! @file
+@brief The food: a small dot that the snake eats.
+
+The class follows the day-21 lecture on inheritance: `Food` is a `Turtle` that
+sets itself up and moves to a random place. Because it inherits from `Turtle`,
+this module needs `turtle` (and so `tkinter`) when it is imported; the game
+imports it only when it starts, and the tests install a fake `turtle` module
+first.
+"""
+
+import random
+from turtle import Turtle
+
+from snake_game.constants import (
+    FOOD_COLOR,
+    FOOD_SHAPE,
+    FOOD_SIZE,
+    FOOD_SPEED,
+    WALL_LIMIT,
+)
+
+
+def random_coordinate() -> int:
+    """! @brief Pick a random x or y inside the walls.
+
+    All the randomness of the food comes from this one function, so that a test can
+    replace it.
+
+    @return A whole number from `-WALL_LIMIT` to `WALL_LIMIT`.
+    """
+    return random.randint(-WALL_LIMIT, WALL_LIMIT)
+
+
+class Food(Turtle):
+    """! @brief The food, a blue circle at a random place inside the walls."""
+
+    def __init__(self) -> None:
+        """! @brief Set the food up and put it at a random place."""
+        super().__init__()
+        self.shape(FOOD_SHAPE)
+        self.penup()
+        self.shapesize(stretch_wid=FOOD_SIZE, stretch_len=FOOD_SIZE)
+        self.color(FOOD_COLOR)
+        self.speed(FOOD_SPEED)
+        self.refresh()
+
+    def refresh(self) -> None:
+        """! @brief Move the food to a new random place inside the walls."""
+        self.goto(random_coordinate(), random_coordinate())

tests/test_food.py

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+"""Tests of the food, with a fake `Turtle` as its base class."""
+
+import importlib
+import sys
+
+import pytest
+
+from fakes import install_fake_turtle, make_food, script_randint
+from snake_game import constants
+
+
+def test_food_is_a_blue_half_size_circle_with_the_pen_up_and_no_animation(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    food = make_food(monkeypatch)
+
+    assert ("shape", ("circle",)) in food.calls
+    assert ("shapesize", (0.5, 0.5)) in food.calls
+    assert ("color", ("blue",)) in food.calls
+    assert ("speed", ("fastest",)) in food.calls
+    assert "penup" in food.call_names()
+
+
+def test_food_inherits_from_turtle_and_calls_the_base_class_first(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    install_fake_turtle(monkeypatch)
+    module = importlib.import_module("snake_game.food")
+
+    food = module.Food()
+
+    assert issubclass(module.Food, sys.modules["turtle"].Turtle)
+    assert food.calls[0][0] == "shape"  # the base class set up `calls` before
+
+
+def test_food_starts_at_a_random_place(monkeypatch: pytest.MonkeyPatch) -> None:
+    script_randint(monkeypatch, [12, -34])
+
+    food = make_food(monkeypatch)
+
+    assert food.position() == (12, -34)
+
+
+def test_refresh_moves_the_food_to_a_new_random_place(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    script_randint(monkeypatch, [1, 2, 3, 4])
+    food = make_food(monkeypatch)
+
+    food.refresh()
+
+    assert food.position() == (3, 4)
+
+
+def test_random_coordinate_asks_for_a_number_from_wall_to_wall(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    bounds = script_randint(monkeypatch, [7])
+    install_fake_turtle(monkeypatch)
+    module = importlib.import_module("snake_game.food")
+
+    result = module.random_coordinate()
+
+    assert result == 7
+    assert bounds == [(-constants.WALL_LIMIT, constants.WALL_LIMIT)]
+
+
+def test_random_places_are_always_inside_the_walls(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    install_fake_turtle(monkeypatch)
+    module = importlib.import_module("snake_game.food")
+
+    places = [module.random_coordinate() for _ in range(500)]
+
+    wall = constants.WALL_LIMIT
+    assert all(-wall <= place <= wall for place in places)