fix and test for animator

tests/test_animator.py

@@ -0,0 +1,166 @@
+from __future__ import annotations
+
+
+from dataclasses import dataclass
+from unittest.mock import Mock
+
+import pytest
+
+
+from textual._animator import SimpleAnimation
+
+
+class Animatable:
+    """An animatable object."""
+
+    def __init__(self, value):
+        self.value = value
+
+    def blend(self, destination: Animatable, factor: float) -> Animatable:
+        return Animatable(self.value + (destination.value - self.value) * factor)
+
+
+@dataclass
+class AnimateTest:
+    """An object to animate."""
+
+    foo: float | None = 0  # Plain float that may be set to None on final_value
+    bar: Animatable = Animatable(0)  # A mock object supporting the animatable protocol
+
+
+def test_simple_animation():
+    """Test an animation from one float to another."""
+
+    # Thing that may be animated
+    animatable = AnimateTest()
+
+    # Fake wall-clock time
+    time = 100.0
+
+    # Object that does the animation
+    animation = SimpleAnimation(
+        animatable,
+        "foo",
+        time,
+        3.0,
+        start_value=20.0,
+        end_value=50.0,
+        final_value=None,
+        easing=lambda x: x,
+    )
+
+    assert animation(time) is False
+    assert animatable.foo == 20.0
+
+    assert animation(time + 1.0) is False
+    assert animatable.foo == 30.0
+
+    assert animation(time + 2.0) is False
+    assert animatable.foo == 40.0
+
+    assert animation(time + 2.9) is False
+    assert pytest.approx(animatable.foo, 49.0)
+
+    assert animation(time + 3.0) is True  # True to indicate animation is complete
+    assert animatable.foo is None  # This is final_value
+
+    assert animation(time + 3.0) is True
+    assert animatable.foo is None
+
+
+def test_simple_animation_duration_zero():
+    """Test animation handles duration of 0."""
+
+    # Thing that may be animated
+    animatable = AnimateTest()
+
+    # Fake wall-clock time
+    time = 100.0
+
+    # Object that does the animation
+    animation = SimpleAnimation(
+        animatable,
+        "foo",
+        time,
+        0.0,
+        start_value=20.0,
+        end_value=50.0,
+        final_value=50.0,
+        easing=lambda x: x,
+    )
+
+    assert animation(time) is True
+    assert animatable.foo == 50.0
+
+    assert animation(time + 1.0) is True
+    assert animatable.foo == 50.0
+
+
+def test_simple_animation_reverse():
+    """Test an animation from one float to another, where the end value is less than the start."""
+
+    # Thing that may be animated
+    animatable = AnimateTest()
+
+    # Fake wall-clock time
+    time = 100.0
+
+    # Object that does the animation
+    animation = SimpleAnimation(
+        animatable,
+        "foo",
+        time,
+        3.0,
+        start_value=50.0,
+        end_value=20.0,
+        final_value=20.0,
+        easing=lambda x: x,
+    )
+
+    assert animation(time) is False
+    assert animatable.foo == 50.0
+
+    assert animation(time + 1.0) is False
+    assert animatable.foo == 40.0
+
+    assert animation(time + 2.0) is False
+    assert animatable.foo == 30.0
+
+    assert animation(time + 3.0) is True
+    assert animatable.foo == 20.0
+
+
+def test_animatable():
+    """Test SimpleAnimation works with the Animatable protocol"""
+
+    animatable = AnimateTest()
+
+    # Fake wall-clock time
+    time = 100.0
+
+    # Object that does the animation
+    animation = SimpleAnimation(
+        animatable,
+        "bar",
+        time,
+        3.0,
+        start_value=Animatable(20.0),
+        end_value=Animatable(50.0),
+        final_value=Animatable(50.0),
+        easing=lambda x: x,
+    )
+
+    assert animation(time) is False
+    assert animatable.bar.value == 20.0
+
+    assert animation(time + 1.0) is False
+    assert animatable.bar.value == 30.0
+
+    assert animation(time + 2.0) is False
+    assert animatable.bar.value == 40.0
+
+    assert animation(time + 2.9) is False
+    assert pytest.approx(animatable.bar.value, 49.0)
+
+    assert animation(time + 3.0) is True  # True to indicate animation is complete
+    assert animatable.bar.value == 50.0