Read and write the high score file and show the stored high score

Refs #24
Refs #25
Refs #26
Task: MIL-004#2
Task: MIL-004#3
Task: MIL-004#4

tests/fakes.py

@@ -286,16 +286,23 @@ def make_food(monkeypatch: pytest.MonkeyPatch) -> Any:
     return module.Food()
 
 
-def make_scoreboard(monkeypatch: pytest.MonkeyPatch) -> Any:
+def make_scoreboard(
+    monkeypatch: pytest.MonkeyPatch, path: str | Path | None = None
+) -> Any:
     """Make a real `Scoreboard` whose base class is the fake `Turtle`.
 
+    When `path` is given it is the high score file; otherwise the default
+    `data.txt` is used, which `conftest.py` has moved into a temporary directory.
+
     The result is typed `Any` because it has the methods of `Scoreboard`
     (`increase_score`) and the recording methods of the fake base class (`calls`)
     at once.
     """
     install_fake_turtle(monkeypatch)
     module = importlib.import_module("snake_game.scoreboard")
-    return module.Scoreboard()
+    if path is None:
+        return module.Scoreboard()
+    return module.Scoreboard(str(path))
 
 
 def imports_turtle_or_tkinter(module_name: str) -> bool:

tests/test_high_score_file.py

@@ -0,0 +1,94 @@
+"""Tests of reading and writing the high score file, with temporary files."""
+
+from pathlib import Path
+
+from snake_game.high_score_file import read_high_score, write_high_score
+
+
+def test_read_returns_the_stored_number(tmp_path: Path) -> None:
+    path = tmp_path / "data.txt"
+    path.write_text("17", encoding="utf-8")
+
+    assert read_high_score(str(path)) == 17
+
+
+def test_read_accepts_a_trailing_newline(tmp_path: Path) -> None:
+    path = tmp_path / "data.txt"
+    path.write_text("5\n", encoding="utf-8")
+
+    assert read_high_score(str(path)) == 5
+
+
+def test_read_creates_a_missing_file_holding_0(tmp_path: Path) -> None:
+    path = tmp_path / "data.txt"
+
+    assert read_high_score(str(path)) == 0
+    assert path.read_text(encoding="utf-8") == "0"
+
+
+def test_read_gives_0_for_an_empty_file_and_leaves_it_empty(tmp_path: Path) -> None:
+    path = tmp_path / "data.txt"
+    path.write_text("", encoding="utf-8")
+
+    assert read_high_score(str(path)) == 0
+    assert path.read_text(encoding="utf-8") == ""
+
+
+def test_read_gives_0_for_text_that_is_not_a_whole_number(tmp_path: Path) -> None:
+    path = tmp_path / "data.txt"
+    path.write_text("many", encoding="utf-8")
+
+    assert read_high_score(str(path)) == 0
+    assert path.read_text(encoding="utf-8") == "many"
+
+
+def test_read_gives_0_for_a_negative_number(tmp_path: Path) -> None:
+    path = tmp_path / "data.txt"
+    path.write_text("-4", encoding="utf-8")
+
+    assert read_high_score(str(path)) == 0
+    assert path.read_text(encoding="utf-8") == "-4"
+
+
+def test_read_gives_0_for_bytes_that_are_not_utf_8(tmp_path: Path) -> None:
+    path = tmp_path / "data.txt"
+    path.write_bytes(b"\xff\xfe\x00\x80")
+
+    assert read_high_score(str(path)) == 0
+    assert path.read_bytes() == b"\xff\xfe\x00\x80"
+
+
+def test_write_replaces_the_old_content(tmp_path: Path) -> None:
+    path = tmp_path / "data.txt"
+    path.write_text("123456", encoding="utf-8")
+
+    write_high_score(9, str(path))
+
+    assert path.read_text(encoding="utf-8") == "9"
+
+
+def test_write_creates_the_file(tmp_path: Path) -> None:
+    path = tmp_path / "data.txt"
+
+    write_high_score(3, str(path))
+
+    assert path.read_text(encoding="utf-8") == "3"
+
+
+def test_the_file_is_closed_after_reading_and_writing(tmp_path: Path) -> None:
+    path = tmp_path / "data.txt"
+
+    write_high_score(2, str(path))
+    read_high_score(str(path))
+    path.unlink()  # fails on Windows while a handle is still open
+
+    assert not path.exists()
+
+
+def test_the_default_path_is_data_txt_in_the_working_directory(
+    tmp_path: Path,
+) -> None:
+    write_high_score(4)
+
+    assert (tmp_path / "data.txt").read_text(encoding="utf-8") == "4"
+    assert read_high_score() == 4

tests/test_scoreboard.py

@@ -2,6 +2,7 @@
 
 import importlib
 import sys
+from pathlib import Path
 
 import pytest
 
@@ -129,6 +130,85 @@ def test_the_score_text_shows_both_scores_while_playing(
     assert scoreboard.calls[-1][1][0] == "Score: 1 High Score: 2"
 
 
+def test_scoreboard_shows_the_stored_high_score_at_start(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    path = tmp_path / "scores.txt"
+    path.write_text("12", encoding="utf-8")
+
+    scoreboard = make_scoreboard(monkeypatch, path)
+
+    assert scoreboard.high_score == 12
+    assert scoreboard.calls[-1][1][0] == "Score: 0 High Score: 12"
+
+
+def test_a_new_high_score_is_written_to_the_file_on_reset(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    path = tmp_path / "scores.txt"
+    path.write_text("1", encoding="utf-8")
+    scoreboard = make_scoreboard(monkeypatch, path)
+    for _ in range(2):
+        scoreboard.increase_score()
+
+    scoreboard.reset()
+
+    assert path.read_text(encoding="utf-8") == "2"
+
+
+def test_a_lower_score_does_not_write_the_file(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    path = tmp_path / "scores.txt"
+    path.write_text("5", encoding="utf-8")
+    scoreboard = make_scoreboard(monkeypatch, path)
+    scoreboard.increase_score()
+    path.write_text("sentinel", encoding="utf-8")
+
+    scoreboard.reset()
+
+    assert path.read_text(encoding="utf-8") == "sentinel"
+    assert scoreboard.high_score == 5
+
+
+def test_an_equal_score_does_not_write_the_file(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    path = tmp_path / "scores.txt"
+    path.write_text("2", encoding="utf-8")
+    scoreboard = make_scoreboard(monkeypatch, path)
+    scoreboard.increase_score()
+    scoreboard.increase_score()
+    path.write_text("sentinel", encoding="utf-8")
+
+    scoreboard.reset()
+
+    assert path.read_text(encoding="utf-8") == "sentinel"
+
+
+def test_a_missing_file_shows_high_score_0_and_is_created(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    path = tmp_path / "scores.txt"
+
+    scoreboard = make_scoreboard(monkeypatch, path)
+
+    assert scoreboard.calls[-1] == START_TEXT
+    assert path.read_text(encoding="utf-8") == "0"
+
+
+def test_a_damaged_file_shows_high_score_0(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    path = tmp_path / "scores.txt"
+    path.write_text("not a number", encoding="utf-8")
+
+    scoreboard = make_scoreboard(monkeypatch, path)
+
+    assert scoreboard.high_score == 0
+    assert scoreboard.calls[-1] == START_TEXT
+
+
 def test_scoreboard_has_no_game_over_any_more(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None: