fix: AddCache concurrency race (#55) and FluentAssertions dependency leak (#56)

.github/workflows/build.yml

@@ -105,7 +105,9 @@ jobs:
 
       - name: Test with coverage
         # Skip Integration (needs Mongo/Redis) and TimeCritical (wall-clock asserts) tests on shared CI runners.
-        run: dotnet test -c Release --no-build --verbosity normal --filter "(Category!=Integration)&(Category!=TimeCritical)" --collect:"XPlat Code Coverage" --results-directory ./coverage
+        # Microsoft.Testing.Platform (see global.json) — xunit.v3 4.x dropped the VSTest bridge, so the
+        # VSTest --filter expression and --collect:"XPlat Code Coverage" no longer apply here.
+        run: dotnet test -c Release --no-build --filter-not-trait "Category=Integration" --filter-not-trait "Category=TimeCritical" --coverage --coverage-output-format cobertura --results-directory ./coverage
 
       - name: Upload coverage to Codecov
         uses: codecov/codecov-action@v5

.gitignore

@@ -149,6 +149,9 @@ coverage*.json
 coverage*.xml
 coverage*.info
 
+# Microsoft.Testing.Platform coverage output directory (--results-directory ./coverage)
+coverage/
+
 # Visual Studio code coverage results
 *.coverage
 *.coveragexml

Tharga.Cache.Blazor/Tharga.Cache.Blazor.csproj

@@ -37,7 +37,7 @@
     </None>
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="Tharga.Blazor" Version="2.3.0" />
+    <PackageReference Include="Tharga.Blazor" Version="2.3.1" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Tharga.Cache\Tharga.Cache.csproj" />

Tharga.Cache.File.Tests/Tharga.Cache.File.Tests.csproj

@@ -2,27 +2,16 @@
 
   <PropertyGroup>
     <TargetFramework>net10.0</TargetFramework>
+    <OutputType>Exe</OutputType>
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
 
   <ItemGroup>
     <PackageReference Include="FluentAssertions" Version="8.10.0" />
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="10.0.11" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.9.0" />
     <PackageReference Include="Moq" Version="4.20.72" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
-      <PrivateAssets>all</PrivateAssets>
-      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-    </PackageReference>
-    <PackageReference Include="coverlet.msbuild" Version="10.0.1">
-      <PrivateAssets>all</PrivateAssets>
-      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-    </PackageReference>
-    <PackageReference Include="coverlet.collector" Version="10.0.1">
-      <PrivateAssets>all</PrivateAssets>
-      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-    </PackageReference>
-    <PackageReference Include="xunit.v3" Version="3.2.2" />
+    <PackageReference Include="Microsoft.Testing.Extensions.CodeCoverage" Version="18.10.0" />
+    <PackageReference Include="xunit.v3" Version="4.0.0" />
   </ItemGroup>
 
   <ItemGroup>

Tharga.Cache.MongoDB.Tests/Tharga.Cache.MongoDB.Tests.csproj

@@ -2,27 +2,16 @@
 
 	<PropertyGroup>
 		<TargetFramework>net10.0</TargetFramework>
+		<OutputType>Exe</OutputType>
 		<ImplicitUsings>enable</ImplicitUsings>
 	</PropertyGroup>
 
 	<ItemGroup>
 		<PackageReference Include="FluentAssertions" Version="8.10.0" />
 		<PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="10.0.11" />
-		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.9.0" />
 		<PackageReference Include="Moq" Version="4.20.72" />
-		<PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
-			<PrivateAssets>all</PrivateAssets>
-			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-		</PackageReference>
-		<PackageReference Include="coverlet.msbuild" Version="10.0.1">
-			<PrivateAssets>all</PrivateAssets>
-			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-		</PackageReference>
-		<PackageReference Include="coverlet.collector" Version="10.0.1">
-			<PrivateAssets>all</PrivateAssets>
-			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-		</PackageReference>
-		<PackageReference Include="xunit.v3" Version="3.2.2" />
+		<PackageReference Include="Microsoft.Testing.Extensions.CodeCoverage" Version="18.10.0" />
+		<PackageReference Include="xunit.v3" Version="4.0.0" />
 	</ItemGroup>
 
 	<ItemGroup>

Tharga.Cache.Redis.Tests/Tharga.Cache.Redis.Tests.csproj

@@ -2,6 +2,7 @@
 
 	<PropertyGroup>
 		<TargetFramework>net10.0</TargetFramework>
+		<OutputType>Exe</OutputType>
 		<ImplicitUsings>enable</ImplicitUsings>
 		<!-- xUnit1051: TestContext.Current.CancellationToken — stylistic, our tests are short-lived. -->
 		<NoWarn>$(NoWarn);xUnit1051</NoWarn>
@@ -10,21 +11,9 @@
 	<ItemGroup>
 		<PackageReference Include="FluentAssertions" Version="8.10.0" />
 		<PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="10.0.11" />
-		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.9.0" />
 		<PackageReference Include="Moq" Version="4.20.72" />
-		<PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
-			<PrivateAssets>all</PrivateAssets>
-			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-		</PackageReference>
-		<PackageReference Include="coverlet.msbuild" Version="10.0.1">
-			<PrivateAssets>all</PrivateAssets>
-			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-		</PackageReference>
-		<PackageReference Include="coverlet.collector" Version="10.0.1">
-			<PrivateAssets>all</PrivateAssets>
-			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-		</PackageReference>
-		<PackageReference Include="xunit.v3" Version="3.2.2" />
+		<PackageReference Include="Microsoft.Testing.Extensions.CodeCoverage" Version="18.10.0" />
+		<PackageReference Include="xunit.v3" Version="4.0.0" />
 	</ItemGroup>
 
 	<ItemGroup>

Tharga.Cache.Tests/AddCacheConcurrencyTests.cs

@@ -0,0 +1,96 @@
+using FluentAssertions;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+using Tharga.Cache.Persist;
+using Xunit;
+
+namespace Tharga.Cache.Tests;
+
+public class AddCacheConcurrencyTests
+{
+    private const int HostCount = 64;
+
+    private sealed record Marker<T>;
+
+    // Nesting a generic in itself yields as many distinct cache types as needed without
+    // declaring one class per host.
+    private static Type MarkerType(int depth)
+    {
+        var type = typeof(object);
+        for (var i = 0; i < depth; i++)
+        {
+            type = typeof(Marker<>).MakeGenericType(type);
+        }
+
+        return type;
+    }
+
+    private static void RegisterMarker(CacheOptions options, int depth)
+    {
+        typeof(CacheOptions)
+            .GetMethod(nameof(CacheOptions.RegisterType))!
+            .MakeGenericMethod(MarkerType(depth), typeof(IMemory))
+            .Invoke(options, [null]);
+    }
+
+    private static IServiceCollection BuildHost(int depth)
+    {
+        var services = new ServiceCollection();
+        services.AddLogging();
+        services.AddCache(o => RegisterMarker(o, depth));
+        return services;
+    }
+
+    private static IReadOnlyDictionary<Type, CacheTypeOptions> RegisteredTypes(IServiceCollection services)
+    {
+        var options = services
+            .Last(x => x.ServiceType == typeof(IOptions<CacheOptions>))
+            .ImplementationInstance as IOptions<CacheOptions>;
+
+        return options!.Value.GetRegistered();
+    }
+
+    [Fact]
+    public void AddCache_CalledConcurrentlyOnIndependentCollections_DoesNotThrow()
+    {
+        //Arrange
+        var depths = Enumerable.Range(1, HostCount).ToArray();
+
+        //Act
+        var act = () => Parallel.ForEach(depths, depth => BuildHost(depth));
+
+        //Assert
+        act.Should().NotThrow();
+    }
+
+    [Fact]
+    public void AddCache_OnIndependentCollections_DoesNotShareRegistrations()
+    {
+        //Arrange
+        var first = BuildHost(1);
+
+        //Act
+        var second = BuildHost(2);
+
+        //Assert
+        RegisteredTypes(first).Keys.Should().BeEquivalentTo([MarkerType(1)]);
+        RegisteredTypes(second).Keys.Should().BeEquivalentTo([MarkerType(2)]);
+    }
+
+    [Fact]
+    public void AddCache_CalledConcurrently_EachCollectionKeepsOnlyItsOwnType()
+    {
+        //Arrange
+        var depths = Enumerable.Range(1, HostCount).ToArray();
+        var hosts = new IServiceCollection[HostCount];
+
+        //Act
+        Parallel.ForEach(depths, depth => hosts[depth - 1] = BuildHost(depth));
+
+        //Assert
+        foreach (var depth in depths)
+        {
+            RegisteredTypes(hosts[depth - 1]).Keys.Should().BeEquivalentTo([MarkerType(depth)]);
+        }
+    }
+}

Tharga.Cache.Tests/AddCacheIdempotencyTests.cs

@@ -1,22 +1,13 @@
 using FluentAssertions;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
 using Tharga.Cache.Persist;
 using Xunit;
 
 namespace Tharga.Cache.Tests;
 
-public class AddCacheIdempotencyTests : IDisposable
+public class AddCacheIdempotencyTests
 {
-    public AddCacheIdempotencyTests()
-    {
-        CacheRegistrationExtensions.ResetRegistrations();
-    }
-
-    public void Dispose()
-    {
-        CacheRegistrationExtensions.ResetRegistrations();
-    }
-
     [Fact]
     public void AddCache_CalledTwice_WithDifferentTypes_DoesNotThrow()
     {
@@ -54,7 +45,7 @@ public void AddCache_CalledTwice_WithSameType_DoesNotThrow()
     }
 
     [Fact]
-    public void AddCache_CalledTwice_WithSameType_FirstRegistrationWins()
+    public void AddCache_CalledTwice_WithSameType_LatestRegistrationWins()
     {
         //Arrange
         var services = new ServiceCollection();
@@ -66,8 +57,8 @@ public void AddCache_CalledTwice_WithSameType_FirstRegistrationWins()
 
         //Assert
         var provider = services.BuildServiceProvider();
-        var cache = provider.GetRequiredService<ITimeToLiveCache>();
-        cache.Should().NotBeNull();
+        var options = provider.GetRequiredService<IOptions<CacheOptions>>().Value;
+        options.GetRegistered()[typeof(string)].DefaultFreshSpan.Should().Be(TimeSpan.FromMinutes(99));
     }
 
     [Fact]

Tharga.Cache.Tests/Tharga.Cache.Tests.csproj

@@ -2,6 +2,7 @@
 
 	<PropertyGroup>
 		<TargetFramework>net10.0</TargetFramework>
+		<OutputType>Exe</OutputType>
 		<ImplicitUsings>enable</ImplicitUsings>
 		<!-- xUnit1051: TestContext.Current.CancellationToken — stylistic, our tests are short-lived. -->
 		<NoWarn>$(NoWarn);xUnit1051</NoWarn>
@@ -10,21 +11,9 @@
 	<ItemGroup>
 		<PackageReference Include="FluentAssertions" Version="8.10.0" />
 		<PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="10.0.11" />
-		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.9.0" />
 		<PackageReference Include="Moq" Version="4.20.72" />
-		<PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
-			<PrivateAssets>all</PrivateAssets>
-			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-		</PackageReference>
-		<PackageReference Include="coverlet.msbuild" Version="10.0.1">
-			<PrivateAssets>all</PrivateAssets>
-			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-		</PackageReference>
-		<PackageReference Include="coverlet.collector" Version="10.0.1">
-			<PrivateAssets>all</PrivateAssets>
-			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-		</PackageReference>
-		<PackageReference Include="xunit.v3" Version="3.2.2" />
+		<PackageReference Include="Microsoft.Testing.Extensions.CodeCoverage" Version="18.10.0" />
+		<PackageReference Include="xunit.v3" Version="4.0.0" />
 	</ItemGroup>
 
 	<ItemGroup>

Tharga.Cache/CacheRegistrationExtensions.cs

@@ -10,13 +10,6 @@ namespace Tharga.Cache;
 
 public static class CacheRegistrationExtensions
 {
-    private static readonly Dictionary<Type, CacheTypeOptions> _configuredPersistTypes = new();
-
-    internal static void ResetRegistrations()
-    {
-        _configuredPersistTypes.Clear();
-    }
-
     public static void AddCache(this IServiceCollection serviceCollection, Action<CacheOptions> options = null)
     {
         var o = new CacheOptions
@@ -25,7 +18,7 @@ public static void AddCache(this IServiceCollection serviceCollection, Action<Ca
         };
         options?.Invoke(o);
 
-        AppendPreviousRegistrations(o);
+        AppendPreviousRegistrations(serviceCollection, o);
 
         // Replace IOptions<CacheOptions> on each call so it carries the merged type registrations.
         serviceCollection.RemoveAll<IOptions<CacheOptions>>();
@@ -104,17 +97,23 @@ public static void AddCache(this IServiceCollection serviceCollection, Action<Ca
     }
 
     /// <summary>
-    /// If AddCache is called several times, this method merges all registrations so they can be used in the end.
-    /// First registration wins — duplicate types are silently skipped.
+    /// If AddCache is called several times on the same service collection, this method merges all registrations
+    /// so they can be used in the end. The type registered by this call wins — duplicates from earlier calls are
+    /// silently skipped.
     /// </summary>
-    private static void AppendPreviousRegistrations(CacheOptions o)
+    /// <remarks>
+    /// The accumulated registrations are read back from the service collection rather than from process-wide
+    /// state, so hosts built concurrently in one process neither race nor inherit each other's registrations.
+    /// </remarks>
+    private static void AppendPreviousRegistrations(IServiceCollection serviceCollection, CacheOptions o)
     {
-        var previouslyRegisteredTypes = _configuredPersistTypes.ToArray();
-        foreach (var item in o.GetRegistered())
-        {
-            _configuredPersistTypes.TryAdd(item.Key, item.Value);
-        }
-        foreach (var previouslyRegisteredType in previouslyRegisteredTypes)
+        var previous = serviceCollection
+            .LastOrDefault(x => x.ServiceType == typeof(IOptions<CacheOptions>))?
+            .ImplementationInstance as IOptions<CacheOptions>;
+
+        if (previous == null) return;
+
+        foreach (var previouslyRegisteredType in previous.Value.GetRegistered())
         {
             o.TryAddType(previouslyRegisteredType.Key, previouslyRegisteredType.Value);
         }

Tharga.Cache/Tharga.Cache.csproj

@@ -53,7 +53,6 @@
 	</ItemGroup>
 
 	<ItemGroup>
-		<PackageReference Include="FluentAssertions" Version="8.10.0" />
 		<PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="10.0.11" />
 		<PackageReference Include="Microsoft.SourceLink.GitHub" Version="10.0.400">
 			<PrivateAssets>all</PrivateAssets>

docs/articles/getting-started.md

@@ -16,6 +16,8 @@ builder.Services.AddCache();
 
 `AddCache` is idempotent — calling it more than once (for example when several libraries each register cache types) merges the registrations instead of throwing.
 
+The merge is scoped to the service collection it is called on, so it is safe to build several hosts concurrently in one process — parallel integration tests each constructing a `WebApplicationFactory`, or a multi-tenant host spinning up isolated containers. Registrations made on one service collection never appear in another.
+
 ## The get-or-load pattern
 
 Inject one of the four cache interfaces and call `GetAsync` with a key and a fetch delegate. The first call runs the delegate and stores the result; subsequent calls within the fresh span return the cached value without invoking the delegate.

global.json

@@ -0,0 +1,5 @@
+{
+  "test": {
+    "runner": "Microsoft.Testing.Platform"
+  }
+}