Ensure Splat initialization in builder and tests

src/Directory.build.props

@@ -17,7 +17,7 @@
     <PackageReleaseNotes>https://github.com/reactiveui/ReactiveUI/releases</PackageReleaseNotes>
     <RepositoryUrl>https://github.com/reactiveui/reactiveui</RepositoryUrl>
     <RepositoryType>git</RepositoryType>
-    <NoWarn>$(NoWarn);IDE0060;IDE1006;IDE0130;VSSpell001</NoWarn>
+    <NoWarn>$(NoWarn);IDE0060;IDE1006;IDE0130;VSSpell001;CA1510</NoWarn>
     <!-- Publish the repository URL in the built .nupkg (in the NuSpec <Repository> element) -->
     <PublishRepositoryUrl>true</PublishRepositoryUrl>
     <!-- Embed source files that are not tracked by the source control manager in the PDB -->
@@ -35,6 +35,8 @@
     <WindowsTargetFrameworks>net462;net472;net8.0-windows10.0.17763.0;net9.0-windows10.0.17763.0;net8.0-windows10.0.19041.0;net9.0-windows10.0.19041.0</WindowsTargetFrameworks>
     <MobileTargetFrameworks>net8.0-android;net8.0-ios;net8.0-tvos;net8.0-macos;net8.0-maccatalyst;net9.0-android;net9.0-ios;net9.0-tvos;net9.0-macos;net9.0-maccatalyst</MobileTargetFrameworks>
     <BaseTargetFrameworks>netstandard2.0;net8.0;net9.0</BaseTargetFrameworks>
+    <!-- Ensure all test runs use our runsettings to control cross-assembly parallelism -->
+    <RunSettingsFilePath>$(MSBuildThisFileDirectory)tests.runsettings</RunSettingsFilePath>
   </PropertyGroup>  
   <PropertyGroup Condition="'$(IsTestProject)' != 'true' and ($(TargetFramework.StartsWith('net8.0')) or $(TargetFramework.StartsWith('net9.0')))">
     <IsAotCompatible>true</IsAotCompatible>

src/ReactiveUI.AOTTests/ComprehensiveAOTTests.cs

@@ -161,6 +161,8 @@ public void ObservableAsPropertyHelper_StringBased_WorksInAOT()
     [Fact]
     public void DependencyInjection_BasicUsage_WorksInAOT()
     {
+        Splat.Builder.AppBuilder.ResetBuilderStateForTests();
+
         // Basic DI operations that work in AOT
         var resolver = Locator.CurrentMutable;
 

src/ReactiveUI.AndroidX/Builder/AndroidXReactiveUIBuilderExtensions.cs

@@ -0,0 +1,54 @@
+// Copyright (c) 2025 .NET Foundation and Contributors. All rights reserved.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using System.Reactive.Concurrency;
+
+namespace ReactiveUI.Builder;
+
+/// <summary>
+/// AndroidX-specific extensions for the ReactiveUI builder.
+/// </summary>
+public static class AndroidXReactiveUIBuilderExtensions
+{
+    /// <summary>
+    /// Gets the android x main thread scheduler.
+    /// </summary>
+    /// <value>
+    /// The android x main thread scheduler.
+    /// </value>
+    public static IScheduler AndroidXMainThreadScheduler { get; } = HandlerScheduler.MainThreadScheduler;
+
+    /// <summary>
+    /// Configures ReactiveUI for AndroidX platform with appropriate schedulers.
+    /// </summary>
+    /// <param name="builder">The builder instance.</param>
+    /// <returns>The builder instance for chaining.</returns>
+    public static ReactiveUIBuilder WithAndroidX(this ReactiveUIBuilder builder)
+    {
+        if (builder is null)
+        {
+            throw new ArgumentNullException(nameof(builder));
+        }
+
+        return builder
+            .WithMainThreadScheduler(HandlerScheduler.MainThreadScheduler)
+            .WithPlatformModule<AndroidX.Registrations>();
+    }
+
+    /// <summary>
+    /// Withes the android x scheduler.
+    /// </summary>
+    /// <param name="builder">The builder.</param>
+    /// <returns>The builder instance for chaining.</returns>
+    public static ReactiveUIBuilder WithAndroidXScheduler(this ReactiveUIBuilder builder)
+    {
+        if (builder is null)
+        {
+            throw new ArgumentNullException(nameof(builder));
+        }
+
+        return builder.WithMainThreadScheduler(AndroidXMainThreadScheduler);
+    }
+}

src/ReactiveUI.Blazor/Builder/BlazorReactiveUIBuilderExtensions.cs

@@ -0,0 +1,52 @@
+// Copyright (c) 2025 .NET Foundation and Contributors. All rights reserved.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+namespace ReactiveUI.Builder;
+
+/// <summary>
+/// Blazor-specific extensions for the ReactiveUI builder.
+/// </summary>
+public static class BlazorReactiveUIBuilderExtensions
+{
+    /// <summary>
+    /// Gets the blazor main thread scheduler.
+    /// </summary>
+    /// <value>
+    /// The blazor main thread scheduler.
+    /// </value>
+    public static IScheduler BlazorMainThreadScheduler { get; } = CurrentThreadScheduler.Instance;
+
+    /// <summary>
+    /// Configures ReactiveUI for Blazor platform with appropriate schedulers.
+    /// </summary>
+    /// <param name="builder">The builder instance.</param>
+    /// <returns>The builder instance for chaining.</returns>
+    public static ReactiveUIBuilder WithBlazor(this ReactiveUIBuilder builder)
+    {
+        if (builder is null)
+        {
+            throw new ArgumentNullException(nameof(builder));
+        }
+
+        return builder
+            .WithBlazorScheduler()
+            .WithPlatformModule<Blazor.Registrations>();
+    }
+
+    /// <summary>
+    /// Withes the blazor scheduler.
+    /// </summary>
+    /// <param name="builder">The builder.</param>
+    /// <returns>The builder instance for chaining.</returns>
+    public static ReactiveUIBuilder WithBlazorScheduler(this ReactiveUIBuilder builder)
+    {
+        if (builder is null)
+        {
+            throw new ArgumentNullException(nameof(builder));
+        }
+
+        return builder.WithMainThreadScheduler(BlazorMainThreadScheduler);
+    }
+}

src/ReactiveUI.Builder.Maui.Tests/ReactiveUIBuilderMauiTests.cs

@@ -3,7 +3,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
 
-using ReactiveUI.Maui;
 using Splat.Builder;
 
 namespace ReactiveUI.Builder.Maui.Tests;
@@ -16,21 +15,7 @@ public void WithMaui_Should_Register_Services()
         AppBuilder.ResetBuilderStateForTests();
         using var locator = new ModernDependencyResolver();
 
-        locator.CreateBuilder()
-               .WithMaui()
-               .Build();
-
-        var typeConverters = locator.GetServices<IBindingTypeConverter>();
-        Assert.NotNull(typeConverters);
-    }
-
-    [Fact]
-    public void WithCoreServices_AndMaui_Should_Register_All_Services()
-    {
-        AppBuilder.ResetBuilderStateForTests();
-        using var locator = new ModernDependencyResolver();
-
-        locator.CreateBuilder()
+        locator.CreateReactiveUIBuilder()
                .WithMaui()
                .Build();
 

src/ReactiveUI.Builder.Tests/Platforms/Blazor/ReactiveUIBuilderBlazorTests.cs

@@ -15,7 +15,7 @@ public void WithBlazor_Should_Register_Services()
     {
         AppBuilder.ResetBuilderStateForTests();
         using var locator = new ModernDependencyResolver();
-        var builder = locator.CreateBuilder();
+        var builder = locator.CreateReactiveUIBuilder();
 
         builder.WithBlazor().Build();
 
@@ -31,9 +31,9 @@ public void WithCoreServices_AndBlazor_Should_Register_All_Services()
     {
         AppBuilder.ResetBuilderStateForTests();
         using var locator = new ModernDependencyResolver();
-        var builder = locator.CreateBuilder();
+        var builder = locator.CreateReactiveUIBuilder();
 
-        builder.WithCoreServices().WithBlazor().Build();
+        builder.WithBlazor().Build();
 
         var observableProperty = locator.GetService<ICreatesObservableForProperty>();
         Assert.NotNull(observableProperty);

src/ReactiveUI.Builder.Tests/Platforms/Drawing/ReactiveUIBuilderDrawingTests.cs

@@ -15,12 +15,12 @@ public void WithDrawing_Should_Register_Services()
     {
         AppBuilder.ResetBuilderStateForTests();
         using var locator = new ModernDependencyResolver();
-        var builder = locator.CreateBuilder();
+        var builder = locator.CreateReactiveUIBuilder();
 
         builder.WithDrawing().Build();
 
         // Drawing registers bitmap loader in non-NETSTANDARD contexts; we can still assert no exception and core services with chaining
-        locator.CreateBuilder().WithCoreServices().WithDrawing().Build();
+        locator.CreateReactiveUIBuilder().WithDrawing().Build();
         var bindingConverters = locator.GetServices<IBindingTypeConverter>();
         Assert.NotNull(bindingConverters);
     }

src/ReactiveUI.Builder.Tests/Platforms/WinForms/ReactiveUIBuilderWinFormsTests.cs

@@ -15,7 +15,7 @@ public void WithWinForms_Should_Register_WinForms_Services()
     {
         AppBuilder.ResetBuilderStateForTests();
         using var locator = new ModernDependencyResolver();
-        var builder = locator.CreateBuilder();
+        var builder = locator.CreateReactiveUIBuilder();
 
         builder.WithWinForms().Build();
 
@@ -31,9 +31,9 @@ public void WithCoreServices_AndWinForms_Should_Register_All_Services()
     {
         AppBuilder.ResetBuilderStateForTests();
         using var locator = new ModernDependencyResolver();
-        var builder = locator.CreateBuilder();
+        var builder = locator.CreateReactiveUIBuilder();
 
-        builder.WithCoreServices().WithWinForms().Build();
+        builder.WithWinForms().Build();
 
         var observableProperty = locator.GetService<ICreatesObservableForProperty>();
         Assert.NotNull(observableProperty);

src/ReactiveUI.Builder.Tests/Platforms/Wpf/ReactiveUIBuilderWpfTests.cs

@@ -15,7 +15,7 @@ public void WithWpf_Should_Register_Wpf_Services()
     {
         AppBuilder.ResetBuilderStateForTests();
         using var locator = new ModernDependencyResolver();
-        var builder = locator.CreateBuilder();
+        var builder = locator.CreateReactiveUIBuilder();
 
         builder.WithWpf().Build();
 
@@ -31,9 +31,9 @@ public void WithCoreServices_AndWpf_Should_Register_All_Services()
     {
         AppBuilder.ResetBuilderStateForTests();
         using var locator = new ModernDependencyResolver();
-        var builder = locator.CreateBuilder();
+        var builder = locator.CreateReactiveUIBuilder();
 
-        builder.WithCoreServices().WithWpf().Build();
+        builder.WithWpf().Build();
 
         var observableProperty = locator.GetService<ICreatesObservableForProperty>();
         Assert.NotNull(observableProperty);

src/ReactiveUI.Builder.Tests/ReactiveUIBuilderBlockingTests.cs

@@ -18,7 +18,7 @@ public void Build_SetsFlag_AndBlocks_InitializeReactiveUI()
         AppBuilder.ResetBuilderStateForTests();
         using var locator = new ModernDependencyResolver();
 
-        var builder = locator.CreateBuilder();
+        var builder = locator.CreateReactiveUIBuilder();
         builder.WithCoreServices().Build();
 
         locator.InitializeReactiveUI();