Add tests for turn_animation_into_updater with zero/negative run_time

Author: behackl

tests/module/animation/test_updaters.py

@@ -0,0 +1,79 @@
+from __future__ import annotations
+
+import pytest
+
+from manim import Circle, FadeIn
+from manim.animation.updaters.mobject_update_utils import turn_animation_into_updater
+
+
+def test_turn_animation_into_updater_zero_run_time():
+    """Test that turn_animation_into_updater handles zero run_time correctly."""
+    # Create a simple mobject and animation
+    mobject = Circle()
+    animation = FadeIn(mobject, run_time=0)
+
+    # Track updater calls
+    update_calls = []
+    original_updaters = mobject.updaters.copy()
+
+    # Call turn_animation_into_updater
+    result = turn_animation_into_updater(animation)
+
+    # Verify mobject is returned
+    assert result is mobject
+
+    # Get the updater that was added
+    assert len(mobject.updaters) == len(original_updaters) + 1
+    updater = mobject.updaters[-1]
+
+    # Simulate calling the updater
+    updater(mobject, dt=0.1)
+
+    # The updater should have finished and removed itself
+    assert len(mobject.updaters) == len(original_updaters)
+    assert updater not in mobject.updaters
+
+    # Animation should be in finished state
+    assert animation.total_time >= 0
+
+
+def test_turn_animation_into_updater_negative_run_time():
+    """Test that turn_animation_into_updater handles negative run_time correctly."""
+    mobject = Circle()
+    animation = FadeIn(mobject, run_time=-1)
+
+    original_updaters = mobject.updaters.copy()
+
+    # Call turn_animation_into_updater
+    result = turn_animation_into_updater(animation)
+
+    # Get the updater that was added
+    updater = mobject.updaters[-1]
+
+    # Simulate calling the updater
+    updater(mobject, dt=0.1)
+
+    # The updater should have finished and removed itself
+    assert len(mobject.updaters) == len(original_updaters)
+    assert updater not in mobject.updaters
+
+
+def test_turn_animation_into_updater_positive_run_time_persists():
+    """Test that updater persists with positive run_time."""
+    mobject = Circle()
+    animation = FadeIn(mobject, run_time=1.0)
+
+    original_updaters = mobject.updaters.copy()
+
+    # Call turn_animation_into_updater
+    result = turn_animation_into_updater(animation)
+
+    # Get the updater that was added
+    updater = mobject.updaters[-1]
+
+    # Simulate calling the updater (partial progress)
+    updater(mobject, dt=0.1)
+
+    # The updater should still be present (not finished)
+    assert len(mobject.updaters) == len(original_updaters) + 1
+    assert updater in mobject.updaters