proejct commit

tests/physics/test_timestep.py

@@ -0,0 +1,57 @@
+"""Tests des festen Zeitschritts (Akkumulator)."""
+
+import pytest
+
+from sandbox.physics import FixedTimestep
+
+STEP = 1 / 120
+
+
+def test_a_60_fps_frame_runs_two_physics_steps() -> None:
+    timestep = FixedTimestep(STEP, max_steps_per_frame=8)
+    assert timestep.advance(1 / 60) == 2
+    assert timestep.alpha == pytest.approx(0, abs=1e-6)
+
+
+def test_short_frames_accumulate() -> None:
+    timestep = FixedTimestep(STEP, max_steps_per_frame=8)
+    assert timestep.advance(1 / 240) == 0
+    assert timestep.alpha == pytest.approx(0.5)
+    assert timestep.advance(1 / 240) == 1
+
+
+def test_no_steps_are_lost_through_rounding() -> None:
+    timestep = FixedTimestep(STEP, max_steps_per_frame=8)
+    total = sum(timestep.advance(1 / 60) for _ in range(1000))
+    assert total == 2000
+
+
+def test_alpha_stays_in_the_unit_interval() -> None:
+    timestep = FixedTimestep(STEP, max_steps_per_frame=8)
+    for frame in (0.003, 0.011, 0.017, 0.0001, 0.02):
+        timestep.advance(frame)
+        assert 0 <= timestep.alpha < 1
+
+
+def test_huge_frames_are_capped_to_avoid_the_spiral_of_death() -> None:
+    timestep = FixedTimestep(STEP, max_steps_per_frame=5)
+    assert timestep.advance(2.0) == 5
+    assert timestep.alpha == 0  # der Rückstand wurde verworfen
+    assert timestep.advance(1 / 60) == 2
+
+
+def test_reset_discards_accumulated_time() -> None:
+    timestep = FixedTimestep(STEP, max_steps_per_frame=8)
+    timestep.advance(STEP * 0.9)
+    timestep.reset()
+    assert timestep.alpha == 0
+    assert timestep.advance(STEP * 0.5) == 0
+
+
+def test_invalid_arguments_are_rejected() -> None:
+    with pytest.raises(ValueError, match="positiv"):
+        FixedTimestep(0, 8)
+    with pytest.raises(ValueError, match="mindestens"):
+        FixedTimestep(STEP, 0)
+    with pytest.raises(ValueError, match="negativ"):
+        FixedTimestep(STEP, 8).advance(-0.1)