Add the Player class and the Up key binding

Task: MIL-003#1
Task: MIL-003#2
Task: MIL-003#3

tests/test_player.py

@@ -0,0 +1,33 @@
+"""Tests for the Player class (need a display; skipped without one)."""
+
+import pytest
+
+from constants import MOVE_DISTANCE, STARTING_POSITION
+from player import Player
+
+
+@pytest.fixture
+def player(screen) -> Player:
+    new_player = Player()
+    yield new_player
+    new_player.hideturtle()
+
+
+def test_player_starts_at_starting_position(player: Player) -> None:
+    assert player.position() == STARTING_POSITION
+
+
+def test_player_faces_north(player: Player) -> None:
+    assert player.heading() == 90
+
+
+def test_go_up_moves_forward_by_move_distance(player: Player) -> None:
+    start_y = player.ycor()
+    player.go_up()
+    assert player.ycor() == start_y + MOVE_DISTANCE
+
+
+def test_go_up_never_moves_sideways(player: Player) -> None:
+    for _ in range(5):
+        player.go_up()
+    assert player.xcor() == pytest.approx(STARTING_POSITION[0])