Added a test case for https://github.com/Cysharp/UniTask/issues/444

src/UniTask/Assets/Tests/AsyncReactivePropertyTest.cs

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+using Cysharp.Threading.Tasks;
+using FluentAssertions;
+using System;
+using System.Collections;
+using System.Threading;
+using UnityEngine.TestTools;
+
+namespace Cysharp.Threading.TasksTests
+{
+    public class AsyncReactivePropertyTest
+    {
+        private int _callCounter;
+        
+        [UnityTest]
+        public IEnumerator WaitCancelWait() => UniTask.ToCoroutine(async () =>
+        {
+            // Test case for https://github.com/Cysharp/UniTask/issues/444
+            
+            var property = new AsyncReactiveProperty<int>(0);
+            
+            var cts1 = new CancellationTokenSource();
+            var cts2 = new CancellationTokenSource();
+            WaitForProperty(property, cts1.Token);
+            WaitForProperty(property, cts2.Token);
+
+            _callCounter = 0;
+            property.Value = 1;
+            _callCounter.Should().Be(2);
+
+            cts2.Cancel();
+            cts2.Dispose();
+            cts1.Cancel();
+            cts1.Dispose();
+
+            var cts3 = new CancellationTokenSource();
+            WaitForProperty(property, cts3.Token);
+
+            _callCounter = 0;
+            property.Value = 2;
+            _callCounter.Should().Be(1);
+            
+            cts3.Cancel();
+            cts3.Dispose();
+            await UniTask.CompletedTask;
+        });
+
+        private async void WaitForProperty(AsyncReactiveProperty<int> property, CancellationToken token)
+        {
+            while (true)
+            {
+                try
+                {
+                    await property.WaitAsync(token);
+                    _callCounter++;
+                }
+                catch (OperationCanceledException)
+                {
+                    break;
+                }
+            }
+        }
+    }
+}

src/UniTask/Assets/Tests/AsyncReactivePropertyTest.cs.meta

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+fileFormatVersion: 2
+guid: 27665955eefb4448969b8cc4dd204600
+timeCreated: 1676129650