Add game data, art, constants and game logic

Add the assignment data set (50 accounts), the logo and vs art, the
constants module, and the pure functions get_random_account,
pick_pair, format_data and check_answer, all with Doxygen comments.
pick_pair never returns the same account twice; check_answer accepts
either choice on a tie. Cover them with pytest tests (22 passing).

The art is built from concatenated raw lines so the backslashes survive
and Doxygen does not read the backticks as markup.

Accept MIL-002 after review RC-005 and add it to the Traceability
Matrix.

Task: MIL-002#1
Task: MIL-002#2
Task: MIL-002#3
Task: MIL-002#4
Task: MIL-002#5
Task: MIL-002#6
Closes #6
Closes #7
Closes #8
Closes #9
Closes #10
Closes #11

tests/test_game_data.py

@@ -0,0 +1,46 @@
+"""@file test_game_data.py
+@brief Tests for the assignment data set and art.
+"""
+
+from higher_lower.art import logo, vs
+from higher_lower.constants import (
+    KEY_COUNTRY,
+    KEY_DESCRIPTION,
+    KEY_FOLLOWER_COUNT,
+    KEY_NAME,
+)
+from higher_lower.game_data import data
+
+EXPECTED_KEYS = {KEY_NAME, KEY_FOLLOWER_COUNT, KEY_DESCRIPTION, KEY_COUNTRY}
+
+
+def test_data_has_fifty_accounts() -> None:
+    """@brief The assignment data set has 50 entries."""
+    assert len(data) == 50
+
+
+def test_every_account_has_the_required_keys() -> None:
+    """@brief Every entry has exactly the four assignment keys."""
+    assert all(set(account) == EXPECTED_KEYS for account in data)
+
+
+def test_follower_counts_are_positive_integers() -> None:
+    """@brief Follower counts are positive integers."""
+    assert all(
+        isinstance(account[KEY_FOLLOWER_COUNT], int) and account[KEY_FOLLOWER_COUNT] > 0
+        for account in data
+    )
+
+
+def test_account_names_are_unique() -> None:
+    """@brief No account appears twice."""
+    names = [account[KEY_NAME] for account in data]
+    assert len(names) == len(set(names))
+
+
+def test_art_is_available() -> None:
+    """@brief The logo and the vs art keep their shape, including backslashes."""
+    assert len(logo.splitlines()) == 10
+    assert "\\" in logo
+    assert len(vs.splitlines()) == 6
+    assert "|___/____(_)" in vs

tests/test_game_logic.py

@@ -0,0 +1,89 @@
+"""@file test_game_logic.py
+@brief Tests for the pure game functions.
+"""
+
+import random
+
+import pytest
+
+from higher_lower.constants import KEY_NAME
+from higher_lower.game_data import Account, data
+from higher_lower.game_logic import (
+    check_answer,
+    format_data,
+    get_random_account,
+    pick_pair,
+)
+
+
+def test_get_random_account_returns_an_entry_of_the_data() -> None:
+    """@brief The drawn account comes from the data set."""
+    assert get_random_account(rng=random.Random(1)) in data
+
+
+def test_get_random_account_is_repeatable_with_a_seed() -> None:
+    """@brief The same seed draws the same account."""
+    assert get_random_account(rng=random.Random(7)) == get_random_account(
+        rng=random.Random(7)
+    )
+
+
+def test_pick_pair_never_returns_the_same_account() -> None:
+    """@brief A and B are always different entries."""
+    rng = random.Random(0)
+    for _ in range(200):
+        first, second = pick_pair(rng=rng)
+        assert first[KEY_NAME] != second[KEY_NAME]
+
+
+def test_pick_pair_with_two_accounts_returns_both() -> None:
+    """@brief With only two accounts, the pair holds both of them."""
+    two = data[:2]
+    first, second = pick_pair(two, random.Random(3))
+    assert {first[KEY_NAME], second[KEY_NAME]} == {a[KEY_NAME] for a in two}
+
+
+def test_pick_pair_with_one_account_raises() -> None:
+    """@brief A pair cannot be drawn from a single account."""
+    with pytest.raises(ValueError):
+        pick_pair(data[:1])
+
+
+def test_format_data_describes_the_account() -> None:
+    """@brief The description holds name, description and country."""
+    account: Account = {
+        "name": "Nike",
+        "follower_count": 109,
+        "description": "Sportswear multinational",
+        "country": "United States",
+    }
+    assert (
+        format_data(account)
+        == "Nike, a Sportswear multinational, from United States"
+    )
+
+
+@pytest.mark.parametrize(
+    ("guess", "a_followers", "b_followers", "expected"),
+    [
+        ("a", 200, 100, True),
+        ("a", 100, 200, False),
+        ("b", 100, 200, True),
+        ("b", 200, 100, False),
+        ("A", 200, 100, True),
+        ("B", 100, 200, True),
+        ("a", 100, 100, True),
+        ("b", 100, 100, True),
+    ],
+)
+def test_check_answer(
+    guess: str, a_followers: int, b_followers: int, expected: bool
+) -> None:
+    """@brief The answer is right for the higher account, and for either on a tie."""
+    assert check_answer(guess, a_followers, b_followers) is expected
+
+
+def test_check_answer_rejects_an_unknown_choice() -> None:
+    """@brief A guess other than a or b is an error."""
+    with pytest.raises(ValueError):
+        check_answer("c", 1, 2)