test: xUnit test project for Feedforward blocks (DeadTimeBuffer/RateLimiter/FirstOrderLag)

tests/ExperionCrawler.Tests/ExperionCrawler.Tests.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.0" />
+    <PackageReference Include="xunit" Version="2.4.2" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+    <PackageReference Include="coverlet.collector" Version="6.0.0">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Web\ExperionCrawler.csproj" />
+  </ItemGroup>
+
+</Project>

tests/ExperionCrawler.Tests/FeedforwardBlocksTests.cs

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+using ExperionCrawler.Infrastructure.Control;
+using Xunit;
+
+public class FeedforwardBlocksTests
+{
+    [Fact]
+    public void DeadTime_delays_by_n_samples()
+    {
+        var d = new DeadTimeBuffer();
+        Assert.Equal(10.0, d.Through(10, 10, 2), 3);
+        for (int i = 0; i < 4; i++)
+            Assert.Equal(10.0, d.Through(20, 10, 2), 3);
+        Assert.Equal(10.0, d.Through(20, 10, 2), 3);
+        Assert.Equal(20.0, d.Through(20, 10, 2), 3);
+    }
+
+    [Fact]
+    public void DeadTime_asymmetric_theta_preserves_history()
+    {
+        // 비대칭 θ(20↔10) 토글 시에도 지연선이 리셋되지 않아야 한다.
+        var d = new DeadTimeBuffer();
+        double ts = 2;
+        for (int i = 0; i < 12; i++) d.Through(0, 20, ts);   // θ=20 → n=10, 0으로 채움
+        // 입력을 100으로 바꾸고 θ를 작은 값으로 토글 — 재시드 버그면 즉시 100 누출
+        Assert.Equal(0.0, d.Through(100, 10, ts), 3);        // n=5 지연 → 아직 0
+        Assert.Equal(0.0, d.Through(100, 20, ts), 3);        // θ 되돌려도 0 (히스토리 보존)
+    }
+
+    [Fact]
+    public void RateLimiter_clamps_asymmetric_up_down()
+    {
+        var r = new RateLimiter();
+        r.Seed(0);
+        Assert.Equal(1, r.Step(100, 60, 600, 1), 3);
+        r.Seed(100);
+        Assert.Equal(90, r.Step(0, 60, 600, 1), 3);
+    }
+
+    [Fact]
+    public void FirstOrderLag_reaches_63pct_after_tau()
+    {
+        var l = new FirstOrderLag();
+        l.Seed(0);
+        double y = 0; double ts = 1, tau = 10;
+        for (int i = 0; i < 10; i++) y = l.Step(1.0, tau, ts);
+        Assert.InRange(y, 0.60, 0.66);
+    }
+}

tests/ExperionCrawler.Tests/GlobalUsings.cs

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+global using Xunit;