more tests

src/textual/pilot.py

@@ -41,6 +41,7 @@ class Pilot:
             delay (float, optional): Seconds to pause. Defaults to 50ms.
         """
         await asyncio.sleep(delay)
+        await asyncio.sleep(0)
 
     async def wait_for_animation(self) -> None:
         """Wait for any animation to complete."""

tests/test_animation.py

@@ -1,4 +1,6 @@
+import asyncio
 from time import time
+
 from textual.app import App, ComposeResult
 from textual.widgets import Static
 
@@ -25,9 +27,19 @@ async def test_animate_height() -> None:
     async with app.run_test() as pilot:
         static = app.query_one(Static)
         assert static.size.height == 1
-        static.styles.animate("height", 100, duration=0.5)
+        static.styles.animate("height", 100, duration=0.5, easing="linear")
         start = time()
+        # Wait for half the animation
+        await pilot.pause(0.25)
+        # Check we reached the half way point
+        assert static.styles.height.value >= 50
+        elapsed = time() - start
+        # Check at least that much time has elapsed
+        assert 0.5 > elapsed > 0.25
+        # Wait for the animation to finished
         await pilot.wait_for_animation()
         elapsed = time() - start
+        # Check that the full time has elapsed
         assert elapsed > 0.5
+        # Check the height reached the maximum
         assert static.styles.height.value == 100