Adopt the Scoreboard class and its tests

Copied unchanged from the base: class Scoreboard(Turtle) with update_scoreboard, increase_score and game_over. MIL-003 checks the values against the day-21 lectures.

Task: MIL-002#4
Closes #11

tests/test_scoreboard.py

@@ -0,0 +1,85 @@
+"""Tests of the scoreboard, with a fake `Turtle` as its base class."""
+
+import importlib
+import sys
+
+import pytest
+
+from fakes import install_fake_turtle, make_scoreboard
+from snake_game import constants
+
+START_TEXT = ("write", ("Score: 0", "center", ("Arial", 24, "normal")))
+
+
+def test_scoreboard_is_white_hidden_and_at_the_top_centre(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    scoreboard = make_scoreboard(monkeypatch)
+
+    assert ("color", ("white",)) in scoreboard.calls
+    assert "penup" in scoreboard.call_names()
+    assert "hideturtle" in scoreboard.call_names()
+    assert ("goto", constants.SCOREBOARD_POSITION) in scoreboard.calls
+
+
+def test_scoreboard_inherits_from_turtle(monkeypatch: pytest.MonkeyPatch) -> None:
+    install_fake_turtle(monkeypatch)
+    module = importlib.import_module("snake_game.scoreboard")
+
+    assert issubclass(module.Scoreboard, sys.modules["turtle"].Turtle)
+
+
+def test_scoreboard_starts_by_writing_score_0_centred_in_arial_24(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    scoreboard = make_scoreboard(monkeypatch)
+
+    assert scoreboard.calls[-1] == START_TEXT
+
+
+def test_increase_score_wipes_the_old_text_and_writes_the_new_score(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    scoreboard = make_scoreboard(monkeypatch)
+
+    scoreboard.increase_score()
+
+    assert scoreboard.call_names()[-2:] == ["clear", "write"]
+    assert scoreboard.calls[-1] == (
+        "write",
+        ("Score: 1", "center", ("Arial", 24, "normal")),
+    )
+
+
+def test_every_food_adds_one_to_the_score(monkeypatch: pytest.MonkeyPatch) -> None:
+    scoreboard = make_scoreboard(monkeypatch)
+
+    for _ in range(3):
+        scoreboard.increase_score()
+
+    assert scoreboard.calls[-1][1][0] == "Score: 3"
+
+
+def test_game_over_writes_the_text_at_the_centre_in_the_scoreboard_font(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    scoreboard = make_scoreboard(monkeypatch)
+
+    scoreboard.game_over()
+
+    assert scoreboard.calls[-2:] == [
+        ("goto", constants.GAME_OVER_POSITION),
+        ("write", ("GAME OVER", "center", ("Arial", 24, "normal"))),
+    ]
+
+
+def test_game_over_leaves_the_score_on_the_screen(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    scoreboard = make_scoreboard(monkeypatch)
+    scoreboard.increase_score()
+    calls_before = len(scoreboard.calls)
+
+    scoreboard.game_over()
+
+    assert "clear" not in scoreboard.call_names()[calls_before:]