test(ci): harden scheduling and allocation gates

tests/AcDream.App.Tests/Rendering/CellViewDedupTests.cs

@@ -71,10 +71,9 @@ public class CellViewDedupTests
 
         // Warm the method/JIT before measuring. Duplicate portal emissions are the hot path.
         Assert.False(view.Add(polygon));
-        long before = GC.GetAllocatedBytesForCurrentThread();
-        for (int i = 0; i < 1_000; i++)
-            Assert.False(view.Add(polygon));
-        long allocated = GC.GetAllocatedBytesForCurrentThread() - before;
+        long allocated = ZeroAllocationProbe.MeasureWarmed(
+            () => _ = view.Add(polygon),
+            batchSize: 1_000);
 
         Assert.True(allocated <= 256, $"duplicate probes allocated {allocated:N0} bytes");
     }
@@ -91,13 +90,13 @@ public class CellViewDedupTests
         view.Reset();
         Assert.True(view.Add(polygon));
 
-        long before = GC.GetAllocatedBytesForCurrentThread();
-        for (int i = 0; i < 1_000; i++)
-        {
-            view.Reset();
-            Assert.True(view.Add(polygon));
-        }
-        long allocated = GC.GetAllocatedBytesForCurrentThread() - before;
+        long allocated = ZeroAllocationProbe.MeasureWarmed(
+            () =>
+            {
+                view.Reset();
+                _ = view.Add(polygon);
+            },
+            batchSize: 1_000);
 
         Assert.True(allocated <= 256, $"steady rebuilds allocated {allocated:N0} bytes");
     }

tests/AcDream.App.Tests/Rendering/DirectionalShadowCascadeFitterTests.cs

@@ -138,20 +138,12 @@ public sealed class DirectionalShadowCascadeFitterTests
         DirectionalShadowCascadeFitInput input = CameraInput(
             Vector3.Zero,
             DirectionalShadowQuality.For(DirectionalShadowPreset.High));
-        Span<DirectionalShadowCascade> cascades =
-            stackalloc DirectionalShadowCascade[4];
+        var cascades = new DirectionalShadowCascade[4];
 
-        // Cross the tiered-JIT promotion threshold before taking the thread's
-        // allocation counter; measuring immediately after one call makes the
-        // runtime's compilation bookkeeping look like renderer allocation.
-        for (int i = 0; i < 128; i++)
-            DirectionalShadowCascadeFitter.Fit(in input, cascades);
-        long before = GC.GetAllocatedBytesForCurrentThread();
-        for (int i = 0; i < 100; i++)
-            DirectionalShadowCascadeFitter.Fit(in input, cascades);
-        long after = GC.GetAllocatedBytesForCurrentThread();
-
-        Assert.Equal(0, after - before);
+        ZeroAllocationProbe.AssertAllocatesNothing(
+            "DirectionalShadowCascadeFitter.Fit",
+            () => DirectionalShadowCascadeFitter.Fit(in input, cascades),
+            batchSize: 100);
     }
 
     [Fact]

tests/AcDream.App.Tests/Rendering/DirectionalShadowCasterFrameTests.cs

@@ -465,12 +465,10 @@ public sealed class DirectionalShadowCasterFrameTests
         frame.Build(in query);
         int copies = source.IndexCopies;
 
-        long before = GC.GetAllocatedBytesForCurrentThread();
-        for (int iteration = 0; iteration < 256; iteration++)
-            frame.Build(in query);
-        long allocated = GC.GetAllocatedBytesForCurrentThread() - before;
-
-        Assert.Equal(0, allocated);
+        ZeroAllocationProbe.AssertAllocatesNothing(
+            "DirectionalShadowCasterFrame.Build stable frame",
+            () => frame.Build(in query),
+            batchSize: 256);
         Assert.Equal(1ul, frame.BuildSequence);
         Assert.Equal(copies, source.IndexCopies);
         Assert.Equal(0, frame.Stats.Classifications);
@@ -508,16 +506,16 @@ public sealed class DirectionalShadowCasterFrameTests
             frame.Build(in query);
         }
 
-        long before = GC.GetAllocatedBytesForCurrentThread();
-        for (int iteration = 0; iteration < 64; iteration++)
+        void RefreshDenseFrame()
         {
             for (int index = 0; index < 75; index++)
                 source.PublishTransformChanges(dynamics[index].Id, 1);
             frame.Build(in query);
         }
-        long allocated = GC.GetAllocatedBytesForCurrentThread() - before;
-
-        Assert.Equal(0, allocated);
+        ZeroAllocationProbe.AssertAllocatesNothing(
+            "DirectionalShadowCasterFrame.Build dense changed frame",
+            RefreshDenseFrame,
+            batchSize: 64);
         Assert.True(frame.Stats.DensityBulkRefresh);
         Assert.Equal(75, frame.Stats.DynamicTransformRefreshes);
         Assert.Equal(0, source.ProjectionReads);

tests/AcDream.App.Tests/Rendering/DirectionalShadowTransformBufferSetTests.cs

@@ -54,18 +54,14 @@ public sealed class DirectionalShadowTransformBufferSetTests
             topologyBuildSequence: 7,
             transforms,
             ReadOnlySpan<int>.Empty);
-        long before = GC.GetAllocatedBytesForCurrentThread();
-        for (int iteration = 0; iteration < 256; iteration++)
-        {
-            buffers.Publish(
+        ZeroAllocationProbe.AssertAllocatesNothing(
+            "DirectionalShadowTransformBufferSet.Publish",
+            () => buffers.Publish(
                 warmed,
                 topologyBuildSequence: 7,
                 transforms,
-                ReadOnlySpan<int>.Empty);
-        }
-        long allocated = GC.GetAllocatedBytesForCurrentThread() - before;
-
-        Assert.Equal(0, allocated);
+                ReadOnlySpan<int>.Empty),
+            batchSize: 256);
         Assert.Equal(buffersBefore, device.CreatedBuffers.Count);
         Assert.Equal(uploadsBefore, slotZero.UploadCount);
         Assert.Empty(device.OfKind<GpuRecordedHostStorageVisibility>());

tests/AcDream.App.Tests/Rendering/Gpu/Vk/VulkanDrawBindingStateTests.cs

@@ -38,15 +38,11 @@ public sealed class VulkanDrawBindingStateTests
         var state = new VulkanDrawBindingState();
         state.MarkBound(pipelineLayout: 30, packGeneration: 8);
 
-        long before = GC.GetAllocatedBytesForCurrentThread();
-        for (int iteration = 0; iteration < 10_000; iteration++)
-        {
-            Assert.False(state.RequiresBind(
+        ZeroAllocationProbe.AssertAllocatesNothing(
+            "VulkanDrawBindingState.RequiresBind",
+            () => _ = state.RequiresBind(
                 pipelineLayout: 30,
-                packGeneration: 8));
-        }
-        long allocated = GC.GetAllocatedBytesForCurrentThread() - before;
-
-        Assert.Equal(0, allocated);
+                packGeneration: 8),
+            batchSize: 10_000);
     }
 }

tests/AcDream.App.Tests/Rendering/HostQuiescenceGateTests.cs

@@ -2,21 +2,38 @@ using AcDream.App.Rendering;
 
 namespace AcDream.App.Tests.Rendering;
 
+[Collection(AcDream.App.Tests.ThreadSchedulingCollection.Name)]
 public sealed class HostQuiescenceGateTests
 {
     [Fact]
-    public async Task ExternalStopWaitsForAdmittedCallbackToReturn()
+    public void ExternalStopWaitsForAdmittedCallbackToReturn()
     {
         var gate = new HostQuiescenceGate();
         using var callbackEntered = new ManualResetEventSlim(false);
         using var releaseCallback = new ManualResetEventSlim(false);
         int calls = 0;
-        Task callback = Task.Run(() => gate.Invoke(() =>
+        Exception? callbackError = null;
+        var callbackThread = new Thread(() =>
         {
-            callbackEntered.Set();
-            Assert.True(releaseCallback.Wait(TimeSpan.FromSeconds(5)));
-            calls++;
-        }));
+            try
+            {
+                gate.Invoke(() =>
+                {
+                    callbackEntered.Set();
+                    Assert.True(releaseCallback.Wait(TimeSpan.FromSeconds(5)));
+                    calls++;
+                });
+            }
+            catch (Exception error)
+            {
+                callbackError = error;
+            }
+        })
+        {
+            IsBackground = true,
+            Name = "HostQuiescenceGate admitted callback contract",
+        };
+        callbackThread.Start();
         Assert.True(callbackEntered.Wait(TimeSpan.FromSeconds(5)));
 
         using var stopStarted = new ManualResetEventSlim(false);
@@ -44,13 +61,15 @@ public sealed class HostQuiescenceGateTests
             TimeSpan.FromSeconds(5));
 
         releaseCallback.Set();
-        await callback;
+        bool callbackJoined = callbackThread.Join(TimeSpan.FromSeconds(5));
         bool stopJoined = stopThread.Join(TimeSpan.FromSeconds(5));
         gate.Invoke(() => calls++);
 
         Assert.True(stopStartedInTime, "the dedicated stop thread did not start");
         Assert.True(stopBlockedOnCallback, "stop never waited for the admitted callback");
+        Assert.True(callbackJoined, "the admitted callback did not finish after release");
         Assert.True(stopJoined, "stop did not finish after the callback returned");
+        Assert.Null(callbackError);
         Assert.Null(stopError);
         Assert.Equal(1, calls);
         Assert.False(gate.IsAccepting);

tests/AcDream.App.Tests/Rendering/Packs/AtmosphericGpuTimerSamplingTests.cs

@@ -45,7 +45,6 @@ public sealed class AtmosphericGpuTimerSamplingTests
             frameSerial: 1);
 
         int measured = 0;
-        long before = GC.GetAllocatedBytesForCurrentThread();
         for (long frame = 1; frame <= 10_000; frame++)
         {
             if (AtmosphericGpuTimerSampling.ShouldMeasure(
@@ -55,9 +54,12 @@ public sealed class AtmosphericGpuTimerSamplingTests
                 measured++;
             }
         }
-        long allocated = GC.GetAllocatedBytesForCurrentThread() - before;
-
         Assert.Equal(2_500, measured);
-        Assert.Equal(0, allocated);
+        ZeroAllocationProbe.AssertAllocatesNothing(
+            "AtmosphericGpuTimerSampling.ShouldMeasure",
+            () => _ = AtmosphericGpuTimerSampling.ShouldMeasure(
+                RenderQualitySemantic.Low,
+                frameSerial: 4),
+            batchSize: 10_000);
     }
 }

tests/AcDream.App.Tests/Rendering/Packs/RenderPackAutoRuntimeTests.cs

@@ -383,12 +383,10 @@ public sealed class RenderPackAutoRuntimeTests
         for (int i = 0; i < 128; i++)
             fixture.Observe(1, stable: true);
 
-        long before = GC.GetAllocatedBytesForCurrentThread();
-        for (int i = 0; i < 128; i++)
-            fixture.Observe(1, stable: true);
-        long after = GC.GetAllocatedBytesForCurrentThread();
-
-        Assert.Equal(0, after - before);
+        ZeroAllocationProbe.AssertAllocatesNothing(
+            "RenderPackAutoRuntime stable observation",
+            () => fixture.Observe(1, stable: true),
+            batchSize: 128);
     }
 
     private sealed class Fixture : IDisposable

tests/AcDream.App.Tests/Rendering/Wb/DirectionalShadowPreparedDrawTests.cs

@@ -371,11 +371,10 @@ public sealed class DirectionalShadowPreparedDrawTests
         Assert.Equal([0, 1], product.DynamicTransformSlots.ToArray());
 
         product.RefreshDynamicTransforms(changed);
-        long before = GC.GetAllocatedBytesForCurrentThread();
-        for (int iteration = 0; iteration < 256; iteration++)
-            product.RefreshDynamicTransforms(changed);
-        long allocated = GC.GetAllocatedBytesForCurrentThread() - before;
-        Assert.Equal(0, allocated);
+        ZeroAllocationProbe.AssertAllocatesNothing(
+            "DirectionalShadowPreparedDraws.RefreshDynamicTransforms",
+            () => product.RefreshDynamicTransforms(changed),
+            batchSize: 256);
 
         RenderProjectionRecord wrongId = current with
         {
@@ -508,16 +507,12 @@ public sealed class DirectionalShadowPreparedDrawTests
             product.Transforms[0]);
         AssertMatrixBitsEqual(movedPart * movedRoot, product.Transforms[1]);
 
-        long beforeDense = GC.GetAllocatedBytesForCurrentThread();
-        for (int iteration = 0; iteration < 256; iteration++)
-        {
-            product.RefreshDynamicTransforms(
+        ZeroAllocationProbe.AssertAllocatesNothing(
+            "DirectionalShadowPreparedDraws.RefreshDynamicTransforms dense",
+            () => product.RefreshDynamicTransforms(
                 reversedDenseChanges,
-                denseRefresh: true);
-        }
-        long denseAllocated =
-            GC.GetAllocatedBytesForCurrentThread() - beforeDense;
-        Assert.Equal(0, denseAllocated);
+                denseRefresh: true),
+            batchSize: 256);
 
         Assert.True(product.TryBegin(generation, 14, estimatedInstances: 0));
         product.Complete(generation, 14, in stats);
@@ -619,9 +614,14 @@ public sealed class DirectionalShadowPreparedDrawTests
         RenderSceneGeneration generation = RenderSceneGeneration.FromRaw(9);
 
         BuildVariedTopology(product, generation, buildSequence: 1, drawCount);
-        long before = GC.GetAllocatedBytesForCurrentThread();
-        BuildVariedTopology(product, generation, buildSequence: 2, drawCount);
-        long allocated = GC.GetAllocatedBytesForCurrentThread() - before;
+        ulong buildSequence = 1;
+        long allocated = ZeroAllocationProbe.MeasureWarmed(
+            () => BuildVariedTopology(
+                product,
+                generation,
+                ++buildSequence,
+                drawCount),
+            batchSize: 1);
 
         Assert.Equal(drawCount, product.Stats.PreparedInstances);
         // One small constant covers the sort's comparison-delegate wrapper.

tests/AcDream.App.Tests/Streaming/LandblockStreamerPoolTests.cs

@@ -13,6 +13,7 @@ namespace AcDream.App.Tests.Streaming;
 /// before Far-tier ones within a lane, a pool of one reproduces the serial
 /// pre-#418 behavior, and disposal joins every worker.
 /// </summary>
+[Collection(AcDream.App.Tests.ThreadSchedulingCollection.Name)]
 public sealed class LandblockStreamerPoolTests
 {
     private const int SpinTimeoutMs = 10_000;

tests/AcDream.App.Tests/ThreadSchedulingCollection.cs

@@ -0,0 +1,13 @@
+namespace AcDream.App.Tests;
+
+/// <summary>
+/// Dedicated-thread coordination tests must not compete with the thousands of
+/// parallel App tests for host scheduling time. They verify ordering and
+/// lifecycle contracts, not behavior under an intentionally saturated test
+/// runner.
+/// </summary>
+[CollectionDefinition(Name, DisableParallelization = true)]
+public sealed class ThreadSchedulingCollection
+{
+    public const string Name = "Dedicated thread scheduling";
+}