diff --git a/src/UniTask.NetCore/UniTask.NetCore.csproj b/src/UniTask.NetCore/UniTask.NetCore.csproj
index 6a9b15d..13f90c7 100644
--- a/src/UniTask.NetCore/UniTask.NetCore.csproj
+++ b/src/UniTask.NetCore/UniTask.NetCore.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>netstandard2.1</TargetFramework>
+        <TargetFrameworks>netcoreapp3.1;netstandard2.1</TargetFrameworks>
         <AssemblyName>UniTask</AssemblyName>
         <LangVersion>8.0</LangVersion>
         <RootNamespace>Cysharp.Threading.Tasks</RootNamespace>
diff --git a/src/UniTask.NetCoreSandbox/AllocationCheck.cs b/src/UniTask.NetCoreSandbox/AllocationCheck.cs
new file mode 100644
index 0000000..c594944
--- /dev/null
+++ b/src/UniTask.NetCoreSandbox/AllocationCheck.cs
@@ -0,0 +1,198 @@
+using BenchmarkDotNet.Attributes;
+using System.Linq;
+using BenchmarkDotNet.Configs;
+using BenchmarkDotNet.Diagnosers;
+using BenchmarkDotNet.Exporters;
+using BenchmarkDotNet.Jobs;
+using BenchmarkDotNet.Running;
+using Cysharp.Threading.Tasks;
+using PooledAwait;
+using System;
+using System.Runtime.ExceptionServices;
+using System.Threading.Tasks;
+using System.Threading;
+using System.Runtime.CompilerServices;
+using Cysharp.Threading.Tasks.CompilerServices;
+using System.Collections.Concurrent;
+
+[Config(typeof(BenchmarkConfig))]
+public class AllocationCheck
+{
+    // note: all the benchmarks use Task/Task<T> for the public API, because BenchmarkDotNet
+    // doesn't work reliably with more exotic task-types (even just ValueTask fails); instead,
+    // we'll obscure the cost of the outer awaitable by doing a relatively large number of
+    // iterations, so that we're only really measuring the inner loop
+    private const int InnerOps = 1000;
+
+    [Benchmark(OperationsPerInvoke = InnerOps)]
+    public async Task ViaUniTask()
+    {
+        for (int i = 0; i < InnerOps; i++)
+        {
+            await Core();
+        }
+
+        static async UniTask Core()
+        {
+            await new TestAwaiter(false, UniTaskStatus.Succeeded);
+            await new TestAwaiter(false, UniTaskStatus.Succeeded);
+            await new TestAwaiter(false, UniTaskStatus.Succeeded);
+        }
+    }
+
+    [Benchmark(OperationsPerInvoke = InnerOps)]
+    public async Task<int> ViaUniTaskT()
+    {
+        var sum = 0;
+        for (int i = 0; i < InnerOps; i++)
+        {
+            sum += await Core();
+        }
+        return sum;
+
+        static async UniTask<int> Core()
+        {
+            var a = await new TestAwaiter<int>(false, UniTaskStatus.Succeeded, 10);
+            var b = await new TestAwaiter<int>(false, UniTaskStatus.Succeeded, 10);
+            var c = await new TestAwaiter<int>(false, UniTaskStatus.Succeeded, 10);
+            return 10;
+        }
+    }
+
+    [Benchmark(OperationsPerInvoke = InnerOps)]
+    public Task ViaUniTaskVoid()
+    {
+        for (int i = 0; i < InnerOps; i++)
+        {
+            Core().Forget();
+        }
+        return Task.CompletedTask;
+
+        static async UniTaskVoid Core()
+        {
+            await new TestAwaiter(false, UniTaskStatus.Succeeded);
+            await new TestAwaiter(false, UniTaskStatus.Succeeded);
+            await new TestAwaiter(false, UniTaskStatus.Succeeded);
+        }
+    }
+}
+
+public class TaskTestException : Exception
+{
+
+}
+
+public struct TestAwaiter : ICriticalNotifyCompletion
+{
+    readonly UniTaskStatus status;
+    readonly bool isCompleted;
+
+    public TestAwaiter(bool isCompleted, UniTaskStatus status)
+    {
+        this.isCompleted = isCompleted;
+        this.status = status;
+    }
+
+    public TestAwaiter GetAwaiter() => this;
+
+    public bool IsCompleted => isCompleted;
+
+    public void GetResult()
+    {
+        switch (status)
+        {
+            case UniTaskStatus.Faulted:
+                throw new TaskTestException();
+            case UniTaskStatus.Canceled:
+                throw new OperationCanceledException();
+            case UniTaskStatus.Pending:
+            case UniTaskStatus.Succeeded:
+            default:
+                break;
+        }
+    }
+
+    public void OnCompleted(Action continuation)
+    {
+        ThreadPool.UnsafeQueueUserWorkItem(ThreadPoolWorkItem.Create(continuation), false);
+    }
+
+    public void UnsafeOnCompleted(Action continuation)
+    {
+        ThreadPool.UnsafeQueueUserWorkItem(ThreadPoolWorkItem.Create(continuation), false);
+    }
+
+
+}
+
+public struct TestAwaiter<T> : ICriticalNotifyCompletion
+{
+    readonly UniTaskStatus status;
+    readonly bool isCompleted;
+    readonly T value;
+
+    public TestAwaiter(bool isCompleted, UniTaskStatus status, T value)
+    {
+        this.isCompleted = isCompleted;
+        this.status = status;
+        this.value = value;
+    }
+
+    public TestAwaiter<T> GetAwaiter() => this;
+
+    public bool IsCompleted => isCompleted;
+
+    public T GetResult()
+    {
+        switch (status)
+        {
+            case UniTaskStatus.Faulted:
+                throw new TaskTestException();
+            case UniTaskStatus.Canceled:
+                throw new OperationCanceledException();
+            case UniTaskStatus.Pending:
+            case UniTaskStatus.Succeeded:
+            default:
+                return value;
+        }
+    }
+
+    public void OnCompleted(Action continuation)
+    {
+        ThreadPool.UnsafeQueueUserWorkItem(ThreadPoolWorkItem.Create(continuation), false);
+    }
+
+    public void UnsafeOnCompleted(Action continuation)
+    {
+        ThreadPool.UnsafeQueueUserWorkItem(ThreadPoolWorkItem.Create(continuation), false);
+    }
+}
+
+public sealed class ThreadPoolWorkItem : IThreadPoolWorkItem
+{
+    static readonly ConcurrentQueue<ThreadPoolWorkItem> pool = new ConcurrentQueue<ThreadPoolWorkItem>();
+
+    Action continuation;
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static ThreadPoolWorkItem Create(Action continuation)
+    {
+        if (!pool.TryDequeue(out var item))
+        {
+            item = new ThreadPoolWorkItem();
+        }
+
+        item.continuation = continuation;
+        return item;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public void Execute()
+    {
+        var call = continuation;
+        continuation = null;
+        pool.Enqueue(this);
+
+        call.Invoke();
+    }
+}
\ No newline at end of file
diff --git a/src/UniTask.NetCoreSandbox/Benchmark.cs b/src/UniTask.NetCoreSandbox/Benchmark.cs
new file mode 100644
index 0000000..b47294e
--- /dev/null
+++ b/src/UniTask.NetCoreSandbox/Benchmark.cs
@@ -0,0 +1,283 @@
+using BenchmarkDotNet.Attributes;
+using System.Linq;
+using BenchmarkDotNet.Configs;
+using BenchmarkDotNet.Diagnosers;
+using BenchmarkDotNet.Exporters;
+using BenchmarkDotNet.Jobs;
+using BenchmarkDotNet.Running;
+using Cysharp.Threading.Tasks;
+using PooledAwait;
+using System;
+using System.Runtime.ExceptionServices;
+using System.Threading.Tasks;
+using System.Threading;
+using System.Runtime.CompilerServices;
+using Cysharp.Threading.Tasks.CompilerServices;
+
+//class Program
+//{
+//    static void Main(string[] args)
+//    {
+//        var switcher = new BenchmarkSwitcher(new[]
+//        {
+//            typeof(StandardBenchmark)
+//        });
+
+//#if DEBUG
+//        var b = new StandardBenchmark();
+
+//#else
+//        switcher.Run(args);
+//#endif
+//    }
+//}
+
+public class BenchmarkConfig : ManualConfig
+{
+    public BenchmarkConfig()
+    {
+        AddDiagnoser(MemoryDiagnoser.Default);
+        AddJob(Job.ShortRun.WithLaunchCount(1).WithIterationCount(1).WithWarmupCount(1));
+    }
+}
+
+// borrowed from PooledAwait
+
+[Config(typeof(BenchmarkConfig))]
+[GroupBenchmarksBy(BenchmarkLogicalGroupRule.ByCategory)]
+[CategoriesColumn]
+public class ComparisonBenchmarks
+{
+    // note: all the benchmarks use Task/Task<T> for the public API, because BenchmarkDotNet
+    // doesn't work reliably with more exotic task-types (even just ValueTask fails); instead,
+    // we'll obscure the cost of the outer awaitable by doing a relatively large number of
+    // iterations, so that we're only really measuring the inner loop
+    private const int InnerOps = 1000;
+
+    public bool ConfigureAwait { get; set; } = false;
+
+    [Benchmark(OperationsPerInvoke = InnerOps, Description = ".NET")]
+    [BenchmarkCategory("Task<T>")]
+    public async Task<int> ViaTaskT()
+    {
+        int sum = 0;
+        for (int i = 0; i < InnerOps; i++)
+            sum += await Inner(1, 2).ConfigureAwait(ConfigureAwait);
+        return sum;
+
+        static async Task<int> Inner(int x, int y)
+        {
+            int i = x;
+            await Task.Yield();
+            i *= y;
+            await Task.Yield();
+            return 5 * i;
+        }
+    }
+
+    [Benchmark(OperationsPerInvoke = InnerOps, Description = ".NET")]
+    [BenchmarkCategory("Task")]
+    public async Task ViaTask()
+    {
+        for (int i = 0; i < InnerOps; i++)
+            await Inner().ConfigureAwait(ConfigureAwait);
+
+        static async Task Inner()
+        {
+            await Task.Yield();
+            await Task.Yield();
+        }
+    }
+
+    [Benchmark(OperationsPerInvoke = InnerOps, Description = ".NET")]
+    [BenchmarkCategory("ValueTask<T>")]
+    public async Task<int> ViaValueTaskT()
+    {
+        int sum = 0;
+        for (int i = 0; i < InnerOps; i++)
+            sum += await Inner(1, 2).ConfigureAwait(ConfigureAwait);
+        return sum;
+
+        static async ValueTask<int> Inner(int x, int y)
+        {
+            int i = x;
+            await Task.Yield();
+            i *= y;
+            await Task.Yield();
+            return 5 * i;
+        }
+    }
+
+    [Benchmark(OperationsPerInvoke = InnerOps, Description = ".NET")]
+    [BenchmarkCategory("ValueTask")]
+    public async Task ViaValueTask()
+    {
+        for (int i = 0; i < InnerOps; i++)
+            await Inner().ConfigureAwait(ConfigureAwait);
+
+        static async ValueTask Inner()
+        {
+            await Task.Yield();
+            await Task.Yield();
+        }
+    }
+
+    [Benchmark(OperationsPerInvoke = InnerOps, Description = "Pooled")]
+    [BenchmarkCategory("ValueTask<T>")]
+    public async Task<int> ViaPooledValueTaskT()
+    {
+        int sum = 0;
+        for (int i = 0; i < InnerOps; i++)
+            sum += await Inner(1, 2).ConfigureAwait(ConfigureAwait);
+        return sum;
+
+        static async PooledValueTask<int> Inner(int x, int y)
+        {
+            int i = x;
+            await Task.Yield();
+            i *= y;
+            await Task.Yield();
+            return 5 * i;
+        }
+    }
+
+    [Benchmark(OperationsPerInvoke = InnerOps, Description = "Pooled")]
+    [BenchmarkCategory("ValueTask")]
+    public async Task ViaPooledValueTask()
+    {
+        for (int i = 0; i < InnerOps; i++)
+            await Inner().ConfigureAwait(ConfigureAwait);
+
+        static async PooledValueTask Inner()
+        {
+            await Task.Yield();
+            await Task.Yield();
+        }
+    }
+
+    [Benchmark(OperationsPerInvoke = InnerOps, Description = "Pooled")]
+    [BenchmarkCategory("Task<T>")]
+    public async Task<int> ViaPooledTaskT()
+    {
+        int sum = 0;
+        for (int i = 0; i < InnerOps; i++)
+            sum += await Inner(1, 2).ConfigureAwait(ConfigureAwait);
+        return sum;
+
+        static async PooledTask<int> Inner(int x, int y)
+        {
+            int i = x;
+            await Task.Yield();
+            i *= y;
+            await Task.Yield();
+            return 5 * i;
+        }
+    }
+
+    [Benchmark(OperationsPerInvoke = InnerOps, Description = "Pooled")]
+    [BenchmarkCategory("Task")]
+    public async Task ViaPooledTask()
+    {
+        for (int i = 0; i < InnerOps; i++)
+            await Inner().ConfigureAwait(ConfigureAwait);
+
+        static async PooledTask Inner()
+        {
+            await Task.Yield();
+            await Task.Yield();
+        }
+    }
+
+    // ---
+
+    //[Benchmark(OperationsPerInvoke = InnerOps, Description = "UniTaskVoid")]
+    //[BenchmarkCategory("UniTask")]
+    //public async Task ViaUniTaskVoid()
+    //{
+    //    for (int i = 0; i < InnerOps; i++)
+    //    {
+    //        await Inner();
+    //    }
+
+    //    static async UniTaskVoid Inner()
+    //    {
+    //        await UniTask.Yield();
+    //        await UniTask.Yield();
+    //    }
+    //}
+
+    [Benchmark(OperationsPerInvoke = InnerOps, Description = "UniTask")]
+    [BenchmarkCategory("UniTask")]
+    public async Task ViaUniTask()
+    {
+        for (int i = 0; i < InnerOps; i++)
+        {
+            await Inner();
+        }
+
+        static async UniTask Inner()
+        {
+            await UniTask.Yield();
+            await UniTask.Yield();
+        }
+    }
+
+    [Benchmark(OperationsPerInvoke = InnerOps, Description = "UniTaskT")]
+    [BenchmarkCategory("UniTask")]
+    public async Task<int> ViaUniTaskT()
+    {
+        var sum = 0;
+        for (int i = 0; i < InnerOps; i++)
+        {
+            sum += await Inner(1, 2);
+        }
+        return sum;
+
+        static async UniTask<int> Inner(int x, int y)
+        {
+            int i = x;
+            await UniTask.Yield();
+            i *= y;
+            await UniTask.Yield();
+            return 5 * i;
+        }
+    }
+}
+
+public struct MyAwaiter : ICriticalNotifyCompletion
+{
+    public MyAwaiter GetAwaiter() => this;
+
+    public bool IsCompleted => false;
+
+    public void GetResult()
+    {
+    }
+
+    public void OnCompleted(Action continuation)
+    {
+        continuation();
+    }
+
+    public void UnsafeOnCompleted(Action continuation)
+    {
+        continuation();
+    }
+}
+
+public struct MyTestStateMachine : IAsyncStateMachine
+{
+    public void MoveNext()
+    {
+        //throw new NotImplementedException();
+
+
+
+
+    }
+
+    public void SetStateMachine(IAsyncStateMachine stateMachine)
+    {
+        //throw new NotImplementedException();
+    }
+}
\ No newline at end of file
diff --git a/src/UniTask.NetCoreSandbox/Program.cs b/src/UniTask.NetCoreSandbox/Program.cs
index ee1989e..3961823 100644
--- a/src/UniTask.NetCoreSandbox/Program.cs
+++ b/src/UniTask.NetCoreSandbox/Program.cs
@@ -38,6 +38,94 @@ namespace NetCoreSandbox
     }
 
 
+    public class TaskTestException : Exception
+    {
+
+    }
+
+
+    public struct TestAwaiter : ICriticalNotifyCompletion
+    {
+        readonly UniTaskStatus status;
+        readonly bool isCompleted;
+
+        public TestAwaiter(bool isCompleted, UniTaskStatus status)
+        {
+            this.isCompleted = isCompleted;
+            this.status = status;
+        }
+
+        public TestAwaiter GetAwaiter() => this;
+
+        public bool IsCompleted => isCompleted;
+
+        public void GetResult()
+        {
+            switch (status)
+            {
+                case UniTaskStatus.Faulted:
+                    throw new TaskTestException();
+                case UniTaskStatus.Canceled:
+                    throw new OperationCanceledException();
+                case UniTaskStatus.Pending:
+                case UniTaskStatus.Succeeded:
+                default:
+                    break;
+            }
+        }
+
+        public void OnCompleted(Action continuation)
+        {
+            ThreadPool.QueueUserWorkItem(_ => continuation(), null);
+        }
+
+        public void UnsafeOnCompleted(Action continuation)
+        {
+            ThreadPool.UnsafeQueueUserWorkItem(_ => continuation(), null);
+        }
+    }
+    public struct TestAwaiter<T> : ICriticalNotifyCompletion
+    {
+        readonly UniTaskStatus status;
+        readonly bool isCompleted;
+        readonly T value;
+
+        public TestAwaiter(bool isCompleted, UniTaskStatus status, T value)
+        {
+            this.isCompleted = isCompleted;
+            this.status = status;
+            this.value = value;
+        }
+
+        public TestAwaiter<T> GetAwaiter() => this;
+
+        public bool IsCompleted => isCompleted;
+
+        public T GetResult()
+        {
+            switch (status)
+            {
+                case UniTaskStatus.Faulted:
+                    throw new TaskTestException();
+                case UniTaskStatus.Canceled:
+                    throw new OperationCanceledException();
+                case UniTaskStatus.Pending:
+                case UniTaskStatus.Succeeded:
+                default:
+                    return value;
+            }
+        }
+
+        public void OnCompleted(Action continuation)
+        {
+            ThreadPool.QueueUserWorkItem(_ => continuation(), null);
+        }
+
+        public void UnsafeOnCompleted(Action continuation)
+        {
+            ThreadPool.UnsafeQueueUserWorkItem(_ => continuation(), null);
+        }
+    }
 
 
     public static partial class UnityUIComponentExtensions
@@ -109,26 +197,45 @@ namespace NetCoreSandbox
 
         static async Task Main(string[] args)
         {
-            var foo = await new ZeroAllocAsyncAwaitInDotNetCore().NanikaAsync(1, 2);
-            Console.WriteLine(foo);
+#if !DEBUG
+            BenchmarkDotNet.Running.BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).Run(args);
 
-            var channel = Channel.CreateSingleConsumerUnbounded<int>();
-
-            // Observable.Range(1,10).CombineLatest(
-
-            var cts = new CancellationTokenSource();
-
-            var token = cts.Token;
-
-            await FooAsync(token).ForEachAsync(x => { }, token);
+            //await new ComparisonBenchmarks().ViaUniTaskT();
+            return;
+#endif
 
 
-            // Observable.Range(1,10).CombineLatest(
+            AsyncTest().Forget();
 
+
+            //AsyncTest().Forget();
+
+            // AsyncTest().Forget();
+
+
+            await UniTask.Yield();
+            Console.ReadLine();
+        }
+
+#pragma warning disable CS1998
+
+
+        static async UniTaskVoid AsyncTest()
+        {
+            // empty
+            await new TestAwaiter(false, UniTaskStatus.Succeeded);
+            await new TestAwaiter(true, UniTaskStatus.Succeeded);
+            await new TestAwaiter(false, UniTaskStatus.Succeeded);
+
+
+            Console.WriteLine("foo");
+            //return 10;
         }
 
 
 
+#pragma warning restore CS1998
+
         void Foo()
         {
 
diff --git a/src/UniTask.NetCoreSandbox/UniTask.NetCoreSandbox.csproj b/src/UniTask.NetCoreSandbox/UniTask.NetCoreSandbox.csproj
index c7cf11b..6d531d0 100644
--- a/src/UniTask.NetCoreSandbox/UniTask.NetCoreSandbox.csproj
+++ b/src/UniTask.NetCoreSandbox/UniTask.NetCoreSandbox.csproj
@@ -7,6 +7,8 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="BenchmarkDotNet" Version="0.12.1" />
+    <PackageReference Include="PooledAwait" Version="1.0.49" />
     <PackageReference Include="System.Interactive.Async" Version="4.1.1" />
     <PackageReference Include="System.Reactive" Version="4.4.1" />
   </ItemGroup>
diff --git a/src/UniTask.NetCoreTests/TaskBuilderCases.cs b/src/UniTask.NetCoreTests/TaskBuilderCases.cs
new file mode 100644
index 0000000..fbe056a
--- /dev/null
+++ b/src/UniTask.NetCoreTests/TaskBuilderCases.cs
@@ -0,0 +1,301 @@
+#pragma warning disable CS1998 
+
+using Cysharp.Threading.Tasks;
+using FluentAssertions;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Channels;
+using Cysharp.Threading.Tasks.Linq;
+using System.Threading.Tasks;
+using Xunit;
+using System.Runtime.CompilerServices;
+
+namespace NetCoreTests
+{
+    public class UniTaskBuilderTest
+    {
+        [Fact]
+        public async Task Empty()
+        {
+            await Core();
+
+            static async UniTask Core()
+            {
+            }
+        }
+
+        [Fact]
+        public async Task EmptyThrow()
+        {
+            await Assert.ThrowsAsync<TaskTestException>(async () => await Core());
+
+            static async UniTask Core()
+            {
+                throw new TaskTestException();
+            }
+        }
+
+        [Fact]
+        public async Task Task_Done()
+        {
+            await Core();
+
+            static async UniTask Core()
+            {
+                await new TestAwaiter(true, UniTaskStatus.Succeeded);
+            }
+        }
+
+        [Fact]
+        public async Task Task_Fail()
+        {
+            await Assert.ThrowsAsync<TaskTestException>(async () => await Core());
+
+            static async UniTask Core()
+            {
+                await new TestAwaiter(true, UniTaskStatus.Faulted);
+            }
+        }
+
+        [Fact]
+        public async Task Task_Cancel()
+        {
+            await Assert.ThrowsAsync<OperationCanceledException>(async () => await Core());
+
+            static async UniTask Core()
+            {
+                await new TestAwaiter(true, UniTaskStatus.Canceled);
+            }
+        }
+
+        [Fact]
+        public async Task AwaitUnsafeOnCompletedCall_Task_SetResult()
+        {
+            await Core();
+
+            static async UniTask Core()
+            {
+                await new TestAwaiter(false, UniTaskStatus.Succeeded);
+                await new TestAwaiter(false, UniTaskStatus.Succeeded);
+                await new TestAwaiter(false, UniTaskStatus.Succeeded);
+            }
+        }
+
+        [Fact]
+        public async Task AwaitUnsafeOnCompletedCall_Task_SetException()
+        {
+            await Assert.ThrowsAsync<TaskTestException>(async () => await Core());
+
+            static async UniTask Core()
+            {
+                await new TestAwaiter(false, UniTaskStatus.Succeeded);
+                await new TestAwaiter(false, UniTaskStatus.Faulted);
+                throw new InvalidOperationException();
+            }
+        }
+
+        [Fact]
+        public async Task AwaitUnsafeOnCompletedCall_Task_SetCancelException()
+        {
+            await Assert.ThrowsAsync<OperationCanceledException>(async () => await Core());
+
+            static async UniTask Core()
+            {
+                await new TestAwaiter(false, UniTaskStatus.Succeeded);
+                await new TestAwaiter(false, UniTaskStatus.Canceled);
+                throw new InvalidOperationException();
+            }
+        }
+    }
+
+    public class UniTask_T_BuilderTest
+    {
+        [Fact]
+        public async Task Empty()
+        {
+            (await Core()).Should().Be(10);
+
+            static async UniTask<int> Core()
+            {
+                return 10;
+            }
+        }
+
+        [Fact]
+        public async Task EmptyThrow()
+        {
+            await Assert.ThrowsAsync<TaskTestException>(async () => await Core());
+
+            static async UniTask<int> Core()
+            {
+                throw new TaskTestException();
+            }
+        }
+
+        [Fact]
+        public async Task Task_Done()
+        {
+            (await Core()).Should().Be(10);
+
+            static async UniTask<int> Core()
+            {
+                return await new TestAwaiter<int>(true, UniTaskStatus.Succeeded, 10);
+            }
+        }
+
+        [Fact]
+        public async Task Task_Fail()
+        {
+            await Assert.ThrowsAsync<TaskTestException>(async () => await Core());
+
+            static async UniTask<int> Core()
+            {
+                return await new TestAwaiter<int>(true, UniTaskStatus.Faulted, 10);
+            }
+        }
+
+        [Fact]
+        public async Task Task_Cancel()
+        {
+            await Assert.ThrowsAsync<OperationCanceledException>(async () => await Core());
+
+            static async UniTask<int> Core()
+            {
+                return await new TestAwaiter<int>(true, UniTaskStatus.Canceled, 10);
+            }
+        }
+
+        [Fact]
+        public async Task AwaitUnsafeOnCompletedCall_Task_SetResult()
+        {
+            (await Core()).Should().Be(6);
+
+            static async UniTask<int> Core()
+            {
+                var sum = 0;
+                sum += await new TestAwaiter<int>(false, UniTaskStatus.Succeeded, 1);
+                sum += await new TestAwaiter<int>(false, UniTaskStatus.Succeeded, 2);
+                sum += await new TestAwaiter<int>(false, UniTaskStatus.Succeeded, 3);
+                return sum;
+            }
+        }
+
+        [Fact]
+        public async Task AwaitUnsafeOnCompletedCall_Task_SetException()
+        {
+            await Assert.ThrowsAsync<TaskTestException>(async () => await Core());
+
+            static async UniTask<int> Core()
+            {
+                await new TestAwaiter<int>(false, UniTaskStatus.Succeeded, 10);
+                await new TestAwaiter<int>(false, UniTaskStatus.Faulted, 10);
+                throw new InvalidOperationException();
+            }
+        }
+
+        [Fact]
+        public async Task AwaitUnsafeOnCompletedCall_Task_SetCancelException()
+        {
+            await Assert.ThrowsAsync<OperationCanceledException>(async () => await Core());
+
+            static async UniTask<int> Core()
+            {
+                await new TestAwaiter<int>(false, UniTaskStatus.Succeeded, 10);
+                await new TestAwaiter<int>(false, UniTaskStatus.Canceled, 10);
+                throw new InvalidOperationException();
+            }
+        }
+    }
+
+    public class TaskTestException : Exception
+    {
+
+    }
+
+    public struct TestAwaiter : ICriticalNotifyCompletion
+    {
+        readonly UniTaskStatus status;
+        readonly bool isCompleted;
+
+        public TestAwaiter(bool isCompleted, UniTaskStatus status)
+        {
+            this.isCompleted = isCompleted;
+            this.status = status;
+        }
+
+        public TestAwaiter GetAwaiter() => this;
+
+        public bool IsCompleted => isCompleted;
+
+        public void GetResult()
+        {
+            switch (status)
+            {
+                case UniTaskStatus.Faulted:
+                    throw new TaskTestException();
+                case UniTaskStatus.Canceled:
+                    throw new OperationCanceledException();
+                case UniTaskStatus.Pending:
+                case UniTaskStatus.Succeeded:
+                default:
+                    break;
+            }
+        }
+
+        public void OnCompleted(Action continuation)
+        {
+            ThreadPool.QueueUserWorkItem(_ => continuation(), null);
+        }
+
+        public void UnsafeOnCompleted(Action continuation)
+        {
+            ThreadPool.UnsafeQueueUserWorkItem(_ => continuation(), null);
+        }
+    }
+
+    public struct TestAwaiter<T> : ICriticalNotifyCompletion
+    {
+        readonly UniTaskStatus status;
+        readonly bool isCompleted;
+        readonly T value;
+
+        public TestAwaiter(bool isCompleted, UniTaskStatus status, T value)
+        {
+            this.isCompleted = isCompleted;
+            this.status = status;
+            this.value = value;
+        }
+
+        public TestAwaiter<T> GetAwaiter() => this;
+
+        public bool IsCompleted => isCompleted;
+
+        public T GetResult()
+        {
+            switch (status)
+            {
+                case UniTaskStatus.Faulted:
+                    throw new TaskTestException();
+                case UniTaskStatus.Canceled:
+                    throw new OperationCanceledException();
+                case UniTaskStatus.Pending:
+                case UniTaskStatus.Succeeded:
+                default:
+                    return value;
+            }
+        }
+
+        public void OnCompleted(Action continuation)
+        {
+            ThreadPool.QueueUserWorkItem(_ => continuation(), null);
+        }
+
+        public void UnsafeOnCompleted(Action continuation)
+        {
+            ThreadPool.UnsafeQueueUserWorkItem(_ => continuation(), null);
+        }
+    }
+}