Animation PlaybackBehavior Implementation and Tests.

src/Avalonia.Base/Animation/Animation.cs

@@ -42,6 +42,15 @@ namespace Avalonia.Animation
                 o => o._playbackDirection,
                 (o, v) => o._playbackDirection = v);
 
+        /// <summary>
+        /// Defines the <see cref="PlaybackBehavior"/> property.
+        /// </summary>
+        public static readonly DirectProperty<Animation, PlaybackBehavior> PlaybackBehaviorProperty =
+            AvaloniaProperty.RegisterDirect<Animation, PlaybackBehavior>(
+                nameof(PlaybackBehavior),
+                o => o._playbackBehavior,
+                (o, v) => o._playbackBehavior = v);
+
         /// <summary>
         /// Defines the <see cref="FillMode"/> property.
         /// </summary>
@@ -91,6 +100,7 @@ namespace Avalonia.Animation
         private TimeSpan _duration;
         private IterationCount _iterationCount = new IterationCount(1);
         private PlaybackDirection _playbackDirection;
+        private PlaybackBehavior _playbackBehavior;
         private FillMode _fillMode;
         private Easing _easing = new LinearEasing();
         private TimeSpan _delay = TimeSpan.Zero;
@@ -124,6 +134,18 @@ namespace Avalonia.Animation
             set { SetAndRaise(PlaybackDirectionProperty, ref _playbackDirection, value); }
         }
 
+        /// <summary>
+        /// Gets or sets the playback behavior for this animation.
+        /// When set to <see cref="PlaybackBehavior.Auto"/>, manually started animations and
+        /// animations targeting <see cref="Visual.IsVisibleProperty"/> always play,
+        /// while style-applied animations pause when the control is not visible.
+        /// </summary>
+        public PlaybackBehavior PlaybackBehavior
+        {
+            get { return _playbackBehavior; }
+            set { SetAndRaise(PlaybackBehaviorProperty, ref _playbackBehavior, value); }
+        }
+
         /// <summary>
         /// Gets or sets the value fill mode for this animation.
         /// </summary> 
@@ -192,11 +214,12 @@ namespace Avalonia.Animation
             return null;
         }
 
-        private (IList<IAnimator> Animators, IList<IDisposable> subscriptions) InterpretKeyframes(Animatable control)
+        private (IList<IAnimator> Animators, IList<IDisposable> subscriptions, bool animatesVisibility) InterpretKeyframes(Animatable control)
         {
             var handlerList = new Dictionary<(Type type, AvaloniaProperty Property), Func<IAnimator>>();
             var animatorKeyFrames = new List<AnimatorKeyFrame>();
             var subscriptions = new List<IDisposable>();
+            var animatesVisibility = false;
 
             foreach (var keyframe in Children)
             {
@@ -207,6 +230,9 @@ namespace Avalonia.Animation
                         throw new InvalidOperationException("No Setter property assigned.");
                     }
 
+                    if (setter.Property == Visual.IsVisibleProperty)
+                        animatesVisibility = true;
+
                     var handler = Animation.GetAnimator(setter) ?? GetAnimatorType(setter.Property);
 
                     if (handler == null)
@@ -265,19 +291,30 @@ namespace Avalonia.Animation
                 }
             }
 
-            return (newAnimatorInstances, subscriptions);
+            return (newAnimatorInstances, subscriptions, animatesVisibility);
         }
 
         IDisposable IAnimation.Apply(Animatable control, IClock? clock, IObservable<bool> match, Action? onComplete)
             => Apply(control, clock, match, onComplete);
-        
+
         /// <inheritdoc cref="IAnimation.Apply"/>
-        internal IDisposable Apply(Animatable control, IClock? clock, IObservable<bool> match, Action? onComplete)
+        internal IDisposable Apply(Animatable control, IClock? clock, IObservable<bool> match, Action? onComplete,
+            bool isManuallyStarted = false)
         {
-            var (animators, subscriptions) = InterpretKeyframes(control);
+            var (animators, subscriptions, animatesVisibility) = InterpretKeyframes(control);
+
+            var shouldPauseOnInvisible = _playbackBehavior switch
+            {
+                PlaybackBehavior.Auto => !(animatesVisibility || isManuallyStarted),
+                PlaybackBehavior.Always => false,
+                PlaybackBehavior.OnlyIfVisible => true,
+                _ => throw new InvalidOperationException($"Unknown PlaybackBehavior value: {_playbackBehavior}"),
+            };
+
             if (animators.Count == 1)
             {
-                var subscription = animators[0].Apply(this, control, clock, match, onComplete);
+                var subscription = animators[0].Apply(this, control, clock, match,
+                    onComplete, shouldPauseOnInvisible);
 
                 if (subscription is not null)
                 {
@@ -297,7 +334,8 @@ namespace Avalonia.Animation
                         completionTasks!.Add(tcs.Task);
                     }
 
-                    var subscription = animator.Apply(this, control, clock, match, animatorOnComplete);
+                    var subscription = animator.Apply(this, control, clock, match,
+                        animatorOnComplete, shouldPauseOnInvisible);
 
                     if (subscription is not null)
                     {
@@ -348,7 +386,7 @@ namespace Avalonia.Animation
                 run.TrySetResult(null);
                 subscriptions?.Dispose();
                 cancellation?.Dispose();
-            });
+            }, isManuallyStarted: true);
 
             cancellation = cancellationToken.Register(() =>
             {

src/Avalonia.Base/Animation/AnimationInstance`1.cs

@@ -38,7 +38,9 @@ namespace Avalonia.Animation
         private EventHandler? _visibilityChangedHandler;
         private EventHandler<VisualTreeAttachmentEventArgs>? _detachedHandler;
 
-        public AnimationInstance(Animation animation, Animatable control, Animator<T> animator, IClock baseClock, Action? OnComplete, Func<double, T, T> Interpolator)
+        private readonly bool _shouldPauseOnInvisible;
+
+        public AnimationInstance(Animation animation, Animatable control, Animator<T> animator, IClock baseClock, Action? OnComplete, Func<double, T, T> Interpolator, bool shouldPauseOnInvisible)
         {
             _animator = animator;
             _animation = animation;
@@ -49,6 +51,7 @@ namespace Avalonia.Animation
             _lastInterpValue = default!;
             _firstKFValue = default!;
             _neutralValue = default!;
+            _shouldPauseOnInvisible = shouldPauseOnInvisible;
             FetchProperties();
         }
 
@@ -120,26 +123,29 @@ namespace Avalonia.Animation
 
             if (_targetControl is Visual visual)
             {
-                _visibilityChangedHandler = (_, _) =>
+                if (_shouldPauseOnInvisible)
                 {
-                    if (_clock is null || _clock.PlayState == PlayState.Stop)
-                        return;
-                    if (visual.IsEffectivelyVisible)
-                    {
-                        if (_clock.PlayState == PlayState.Pause)
-                            _clock.PlayState = PlayState.Run;
-                    }
-                    else
+                    _visibilityChangedHandler = (_, _) =>
                     {
-                        if (_clock.PlayState == PlayState.Run)
-                            _clock.PlayState = PlayState.Pause;
-                    }
-                };
-                visual.IsEffectivelyVisibleChanged += _visibilityChangedHandler;
-
-                // If already invisible when animation starts, pause immediately.
-                if (!visual.IsEffectivelyVisible)
-                    _clock.PlayState = PlayState.Pause;
+                        if (_clock is null || _clock.PlayState == PlayState.Stop)
+                            return;
+                        if (visual.IsEffectivelyVisible)
+                        {
+                            if (_clock.PlayState == PlayState.Pause)
+                                _clock.PlayState = PlayState.Run;
+                        }
+                        else
+                        {
+                            if (_clock.PlayState == PlayState.Run)
+                                _clock.PlayState = PlayState.Pause;
+                        }
+                    };
+                    visual.IsEffectivelyVisibleChanged += _visibilityChangedHandler;
+
+                    // If already invisible when animation starts, pause immediately.
+                    if (!visual.IsEffectivelyVisible)
+                        _clock.PlayState = PlayState.Pause;
+                }
 
                 // Stop and dispose the animation when detached from the visual tree.
                 _detachedHandler = (_, _) => DoComplete();

src/Avalonia.Base/Animation/Animators/Animator`1.cs

@@ -17,9 +17,9 @@ namespace Avalonia.Animation.Animators
         public AvaloniaProperty? Property { get; set; }
 
         /// <inheritdoc/>
-        public virtual IDisposable? Apply(Animation animation, Animatable control, IClock? clock, IObservable<bool> match, Action? onComplete)
+        public virtual IDisposable? Apply(Animation animation, Animatable control, IClock? clock, IObservable<bool> match, Action? onComplete, bool shouldPauseOnInvisible)
         {
-            var subject = new DisposeAnimationInstanceSubject<T>(this, animation, control, clock, onComplete);
+            var subject = new DisposeAnimationInstanceSubject<T>(this, animation, control, clock, onComplete, shouldPauseOnInvisible);
             return new CompositeDisposable(match.Subscribe(subject), subject);
         }
 
@@ -103,7 +103,7 @@ namespace Avalonia.Animation.Animators
         /// <summary>
         /// Runs the KeyFrames Animation.
         /// </summary>
-        internal IDisposable Run(Animation animation, Animatable control, IClock? clock, Action? onComplete)
+        internal IDisposable Run(Animation animation, Animatable control, IClock? clock, Action? onComplete, bool shouldPauseOnInvisible)
         {
             var instance = new AnimationInstance<T>(
                 animation,
@@ -111,7 +111,8 @@ namespace Avalonia.Animation.Animators
                 this,
                 clock ?? control.Clock ?? Clock.GlobalClock,
                 onComplete,
-                InterpolationHandler);
+                InterpolationHandler,
+                shouldPauseOnInvisible);
 
             return BindAnimation(control, instance);
         }

src/Avalonia.Base/Animation/Animators/BaseBrushAnimator.cs

@@ -38,20 +38,20 @@ namespace Avalonia.Animation.Animators
 
         /// <inheritdoc/>
         public override IDisposable? Apply(Animation animation, Animatable control, IClock? clock,
-            IObservable<bool> match, Action? onComplete)
+            IObservable<bool> match, Action? onComplete, bool shouldPauseOnInvisible)
         {
             if (TryCreateCustomRegisteredAnimator(out var animator)
                 || TryCreateGradientAnimator(out animator)
                 || TryCreateSolidColorBrushAnimator(out animator))
             {
-                return animator.Apply(animation, control, clock, match, onComplete);
+                return animator.Apply(animation, control, clock, match, onComplete, shouldPauseOnInvisible);
             }
 
             Logger.TryGet(LogEventLevel.Error, LogArea.Animations)?.Log(
                 this,
                 "The animation's keyframe value types set is not supported.");
 
-            return base.Apply(animation, control, clock, match, onComplete);
+            return base.Apply(animation, control, clock, match, onComplete, shouldPauseOnInvisible);
         }
 
         /// <summary>

src/Avalonia.Base/Animation/Animators/TransformAnimator.cs

@@ -14,7 +14,8 @@ namespace Avalonia.Animation.Animators
         DoubleAnimator? _doubleAnimator;
 
         /// <inheritdoc/>
-        public override IDisposable? Apply(Animation animation, Animatable control, IClock? clock, IObservable<bool> obsMatch, Action? onComplete)
+        public override IDisposable? Apply(Animation animation, Animatable control, IClock? clock,
+            IObservable<bool> obsMatch, Action? onComplete, bool shouldPauseOnInvisible)
         {
             var ctrl = (Visual)control;
 
@@ -65,7 +66,8 @@ namespace Avalonia.Animation.Animators
                 // It's a transform object so let's target that.
                 if (renderTransformType == Property.OwnerType)
                 {
-                    return _doubleAnimator.Apply(animation, (Transform) ctrl.RenderTransform, clock ?? control.Clock, obsMatch, onComplete);
+                    return _doubleAnimator.Apply(animation, (Transform) ctrl.RenderTransform, clock ?? control.Clock,
+                        obsMatch, onComplete, shouldPauseOnInvisible);
                 }
                 // It's a TransformGroup and try finding the target there.
                 else if (renderTransformType == typeof(TransformGroup))
@@ -74,7 +76,8 @@ namespace Avalonia.Animation.Animators
                     {
                         if (transform.GetType() == Property.OwnerType)
                         {
-                            return _doubleAnimator.Apply(animation, transform, clock ?? control.Clock, obsMatch, onComplete);
+                            return _doubleAnimator.Apply(animation, transform, clock ?? control.Clock,
+                                obsMatch, onComplete, shouldPauseOnInvisible);
                         }
                     }
                 }

src/Avalonia.Base/Animation/DisposeAnimationInstanceSubject.cs

@@ -6,24 +6,18 @@ namespace Avalonia.Animation
     /// <summary>
     /// Manages the lifetime of animation instances as determined by its selector state.
     /// </summary>
-    internal class DisposeAnimationInstanceSubject<T> : IObserver<bool>, IDisposable
+    internal class DisposeAnimationInstanceSubject<T>(
+        Animator<T> animator,
+        Animation animation,
+        Animatable control,
+        IClock? clock,
+        Action? onComplete,
+        bool shouldPauseOnInvisible)
+        : IObserver<bool>, IDisposable
     {
         private IDisposable? _lastInstance;
         private bool _lastMatch;
-        private readonly Animator<T> _animator;
-        private readonly Animation _animation;
-        private readonly Animatable _control;
-        private readonly Action? _onComplete;
-        private readonly IClock? _clock;
 
-        public DisposeAnimationInstanceSubject(Animator<T> animator, Animation animation, Animatable control, IClock? clock, Action? onComplete)
-        {
-            this._animator = animator;
-            this._animation = animation;
-            this._control = control;
-            this._onComplete = onComplete;
-            this._clock = clock;
-        }
         public void Dispose()
         {
             _lastInstance?.Dispose();
@@ -47,7 +41,7 @@ namespace Avalonia.Animation
 
                 if (matchVal)
                 {
-                    _lastInstance = _animator.Run(_animation, _control, _clock, _onComplete);
+                    _lastInstance = animator.Run(animation, control, clock, onComplete, shouldPauseOnInvisible);
                 }
                 else
                 {

src/Avalonia.Base/Animation/IAnimator.cs

@@ -12,11 +12,12 @@ namespace Avalonia.Animation
         /// <summary>
         /// The target property.
         /// </summary>
-        AvaloniaProperty? Property {get; set;}
+        AvaloniaProperty? Property { get; set; }
 
         /// <summary>
         /// Applies the current KeyFrame group to the specified control.
         /// </summary>
-        IDisposable? Apply(Animation animation, Animatable control, IClock? clock, IObservable<bool> match, Action? onComplete);
+        IDisposable? Apply(Animation animation, Animatable control, IClock? clock,
+            IObservable<bool> match, Action? onComplete, bool shouldPauseOnInvisible);
     }
 }

src/Avalonia.Base/Animation/PlaybackBehavior.cs

@@ -0,0 +1,26 @@
+namespace Avalonia.Animation
+{
+    /// <summary>
+    /// Determines whether an animation pauses when its target control is not visible.
+    /// </summary>
+    public enum PlaybackBehavior
+    {
+        /// <summary>
+        /// The system decides based on context. Manually started animations
+        /// (via <see cref="Animation.RunAsync(Animatable, System.Threading.CancellationToken)"/>)
+        /// and animations that target <see cref="Visual.IsVisibleProperty"/> always play.
+        /// Style-applied animations pause when the control is not effectively visible.
+        /// </summary>
+        Auto,
+
+        /// <summary>
+        /// The animation always plays regardless of the control's visibility state.
+        /// </summary>
+        Always,
+
+        /// <summary>
+        /// The animation pauses when the control is not effectively visible.
+        /// </summary>
+        OnlyIfVisible,
+    }
+}

src/Avalonia.Base/Media/Effects/EffectAnimator.cs

@@ -10,17 +10,17 @@ namespace Avalonia.Animation.Animators;
 internal class EffectAnimator : Animator<IEffect?>
 {
     public override IDisposable? Apply(Animation animation, Animatable control, IClock? clock,
-        IObservable<bool> match, Action? onComplete)
+        IObservable<bool> match, Action? onComplete, bool shouldPauseOnInvisible)
     {
         if (TryCreateAnimator<BlurEffectAnimator, IBlurEffect>(out var animator)
             || TryCreateAnimator<DropShadowEffectAnimator, IDropShadowEffect>(out animator))
-            return animator.Apply(animation, control, clock, match, onComplete);
+            return animator.Apply(animation, control, clock, match, onComplete, shouldPauseOnInvisible);
 
         Logger.TryGet(LogEventLevel.Error, LogArea.Animations)?.Log(
             this,
             "The animation's keyframe value types set is not supported.");
 
-        return base.Apply(animation, control, clock, match, onComplete);
+        return base.Apply(animation, control, clock, match, onComplete, shouldPauseOnInvisible);
     }
 
     private bool TryCreateAnimator<TAnimator, TInterface>([NotNullWhen(true)] out IAnimator? animator)

tests/Avalonia.Base.UnitTests/Animation/AnimationIterationTests.cs

@@ -117,6 +117,9 @@ namespace Avalonia.Base.UnitTests.Animation
                 Delay = TimeSpan.FromSeconds(3),
                 DelayBetweenIterations = TimeSpan.FromSeconds(3),
                 IterationCount = new IterationCount(2),
+                // Explicit opt-in: RunAsync (manual) with Auto resolves to Always,
+                // but this test specifically exercises the pause-on-invisible feature.
+                PlaybackBehavior = PlaybackBehavior.OnlyIfVisible,
                 Children = { keyframe1, keyframe2, keyframe3 }
             };
 
@@ -180,6 +183,9 @@ namespace Avalonia.Base.UnitTests.Animation
                 Delay = TimeSpan.FromSeconds(3),
                 DelayBetweenIterations = TimeSpan.FromSeconds(3),
                 IterationCount = new IterationCount(2),
+                // Explicit opt-in: RunAsync (manual) with Auto resolves to Always,
+                // but this test specifically exercises the pause-on-invisible feature.
+                PlaybackBehavior = PlaybackBehavior.OnlyIfVisible,
                 Children = { keyframe1, keyframe2, keyframe3 }
             };
 
@@ -276,6 +282,9 @@ namespace Avalonia.Base.UnitTests.Animation
             {
                 Duration = TimeSpan.FromSeconds(3),
                 IterationCount = new IterationCount(1),
+                // Explicit opt-in: RunAsync (manual) with Auto resolves to Always,
+                // but this test specifically exercises the pause-on-invisible feature.
+                PlaybackBehavior = PlaybackBehavior.OnlyIfVisible,
                 Children = { keyframe2, keyframe1 }
             };
 
@@ -960,6 +969,206 @@ namespace Avalonia.Base.UnitTests.Animation
             }
         }
 
+        [Fact]
+        public void Animation_Can_Set_IsVisible_True_On_Invisible_Control()
+        {
+            // Reproduces a bug where an expand animation tries to make a collapsed
+            // (invisible) control visible at Cue 0.0, but the animation system pauses
+            // animations on invisible controls, creating a deadlock where the animation
+            // can't run to set IsVisible=true because the control is already invisible.
+            var animation = new Animation()
+            {
+                Duration = TimeSpan.FromSeconds(0.3),
+                FillMode = FillMode.Forward,
+                Children =
+                {
+                    new KeyFrame()
+                    {
+                        Cue = new Cue(0.0),
+                        Setters = { new Setter(Visual.IsVisibleProperty, true) }
+                    },
+                    new KeyFrame()
+                    {
+                        Cue = new Cue(1.0),
+                        Setters = { new Setter(Visual.IsVisibleProperty, true) }
+                    }
+                }
+            };
+
+            // Control starts invisible (collapsed state).
+            var border = new Border() { IsVisible = false };
+
+            var clock = new TestClock();
+            var animationRun = animation.RunAsync(border, clock, TestContext.Current.CancellationToken);
+
+            // Kick off the animation.
+            clock.Step(TimeSpan.Zero);
+
+            // The Cue 0.0 keyframe should have set IsVisible = true,
+            // even though the control started invisible.
+            Assert.True(border.IsVisible);
+
+            // Animation should progress to completion.
+            clock.Step(TimeSpan.FromSeconds(0.3));
+            Assert.True(animationRun.IsCompleted);
+        }
+
+        [Fact]
+        public void Width_Animation_Progresses_After_IsVisible_Set_True_On_Invisible_Control()
+        {
+            // Tests the expand scenario with a double property: the control starts invisible,
+            // and the animation drives Width from 0 to 100. With the pause-on-invisible
+            // behavior, the animation clock should still advance after the control becomes
+            // visible (even if made visible by the same logical expand action).
+            var animation = new Animation()
+            {
+                Duration = TimeSpan.FromSeconds(0.3),
+                Easing = new LinearEasing(),
+                FillMode = FillMode.Forward,
+                Children =
+                {
+                    new KeyFrame()
+                    {
+                        Cue = new Cue(0.0),
+                        Setters = { new Setter(Layoutable.WidthProperty, 0d) }
+                    },
+                    new KeyFrame()
+                    {
+                        Cue = new Cue(1.0),
+                        Setters = { new Setter(Layoutable.WidthProperty, 100d) }
+                    }
+                }
+            };
+
+            // Control starts invisible (collapsed state).
+            var border = new Border() { Width = 0d, IsVisible = false };
+
+            var clock = new TestClock();
+            var animationRun = animation.RunAsync(border, clock, TestContext.Current.CancellationToken);
+
+            clock.Step(TimeSpan.Zero);
+
+            // Simulate what the expand handler does: set IsVisible = true externally.
+            border.IsVisible = true;
+
+            // The animation should now be able to make progress.
+            clock.Step(TimeSpan.FromSeconds(0.3));
+            Assert.True(animationRun.IsCompleted);
+            Assert.Equal(100d, border.Width);
+        }
+
+        [Fact]
+        public void Animation_Can_Set_IsVisible_False_At_End_Without_Pausing_Itself()
+        {
+            // An animation that sets IsVisible=false at Cue 1.0 should complete normally.
+            // The visibility change at the final keyframe should not cause the animation
+            // to pause before it can report completion.
+            var animation = new Animation()
+            {
+                Duration = TimeSpan.FromSeconds(0.3),
+                FillMode = FillMode.Forward,
+                Children =
+                {
+                    new KeyFrame()
+                    {
+                        Cue = new Cue(0.0),
+                        Setters = { new Setter(Visual.IsVisibleProperty, true) }
+                    },
+                    new KeyFrame()
+                    {
+                        Cue = new Cue(1.0),
+                        Setters = { new Setter(Visual.IsVisibleProperty, false) }
+                    }
+                }
+            };
+
+            // Control starts visible (expanded state).
+            var border = new Border() { IsVisible = true };
+
+            var clock = new TestClock();
+            var animationRun = animation.RunAsync(border, clock, TestContext.Current.CancellationToken);
+
+            clock.Step(TimeSpan.Zero);
+            Assert.True(border.IsVisible);
+
+            // Step to the end: animation sets IsVisible=false.
+            clock.Step(TimeSpan.FromSeconds(0.3));
+
+            // Animation should have completed and the final value should hold.
+            Assert.True(animationRun.IsCompleted);
+            Assert.False(border.IsVisible);
+        }
+
+        [Fact]
+        public async Task Cancelling_Expand_Animation_Mid_Flight_Then_Collapsing_Works()
+        {
+            // Reproduces the scenario where a user rapidly toggles expand/collapse:
+            // the first animation is cancelled and a new one starts in the opposite direction.
+            // Uses single-property animations to isolate the visibility behavior.
+            var expandAnimation = new Animation()
+            {
+                Duration = TimeSpan.FromSeconds(0.3),
+                FillMode = FillMode.Forward,
+                Children =
+                {
+                    new KeyFrame()
+                    {
+                        Cue = new Cue(0.0),
+                        Setters = { new Setter(Visual.IsVisibleProperty, true) }
+                    },
+                    new KeyFrame()
+                    {
+                        Cue = new Cue(1.0),
+                        Setters = { new Setter(Visual.IsVisibleProperty, true) }
+                    }
+                }
+            };
+
+            var collapseAnimation = new Animation()
+            {
+                Duration = TimeSpan.FromSeconds(0.3),
+                FillMode = FillMode.Forward,
+                Children =
+                {
+                    new KeyFrame()
+                    {
+                        Cue = new Cue(0.0),
+                        Setters = { new Setter(Visual.IsVisibleProperty, true) }
+                    },
+                    new KeyFrame()
+                    {
+                        Cue = new Cue(1.0),
+                        Setters = { new Setter(Visual.IsVisibleProperty, false) }
+                    }
+                }
+            };
+
+            var border = new Border() { IsVisible = false };
+
+            // Start expand.
+            var cts1 = new CancellationTokenSource();
+            var clock1 = new TestClock();
+            var expandRun = expandAnimation.RunAsync(border, clock1, cts1.Token);
+
+            clock1.Step(TimeSpan.Zero);
+            Assert.True(border.IsVisible);
+
+            // Partially through expand, cancel and start collapse.
+            clock1.Step(TimeSpan.FromSeconds(0.15));
+            cts1.Cancel();
+            await expandRun;
+
+            var cts2 = new CancellationTokenSource();
+            var clock2 = new TestClock();
+            var collapseRun = collapseAnimation.RunAsync(border, clock2, cts2.Token);
+
+            clock2.Step(TimeSpan.Zero);
+            clock2.Step(TimeSpan.FromSeconds(0.3));
+
+            Assert.True(collapseRun.IsCompleted);
+            Assert.False(border.IsVisible);
+        }
+
         private sealed class FakeAnimator : InterpolatingAnimator<double>
         {
             public double LastProgress { get; set; } = double.NaN;