Migrate xUnit + FluentAssertions to NUnit 4.4.0 with Controlled Concurrency and Proper STA Thread Support (#4121)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: glennawatson <5834289+glennawatson@users.noreply.github.com>

Author: Copilot

.editorconfig

@@ -502,6 +502,119 @@ dotnet_diagnostic.RCS1190.severity=error
 dotnet_diagnostic.RCS1195.severity=error
 dotnet_diagnostic.RCS1214.severity=error
 
+[*.{cs,vb}]
+#############################################
+# NUnit Analyzers — enable all as errors
+#############################################
+
+# Structure Rules (NUnit1001 - )
+dotnet_diagnostic.NUnit1001.severity = error # TestCase args must match parameter types
+dotnet_diagnostic.NUnit1002.severity = error # TestCaseSource should use nameof
+dotnet_diagnostic.NUnit1003.severity = error # TestCase provided too few arguments
+dotnet_diagnostic.NUnit1004.severity = error # TestCase provided too many arguments
+dotnet_diagnostic.NUnit1005.severity = error # ExpectedResult type must match return type
+dotnet_diagnostic.NUnit1006.severity = error # ExpectedResult must not be used on void methods
+dotnet_diagnostic.NUnit1007.severity = error # Non-void method but no ExpectedResult provided
+dotnet_diagnostic.NUnit1008.severity = error # ParallelScope.Self at assembly level has no effect
+dotnet_diagnostic.NUnit1009.severity = error # ParallelScope.Children on non-parameterized test
+dotnet_diagnostic.NUnit1010.severity = error # ParallelScope.Fixtures on a test method
+dotnet_diagnostic.NUnit1011.severity = error # TestCaseSource member does not exist
+dotnet_diagnostic.NUnit1012.severity = error # async test method must have non-void return type
+dotnet_diagnostic.NUnit1013.severity = error # async method must use non-generic Task when no result
+dotnet_diagnostic.NUnit1014.severity = error # async method must use Task<T> when result expected
+dotnet_diagnostic.NUnit1015.severity = error # Source type does not implement I(Async)Enumerable
+dotnet_diagnostic.NUnit1016.severity = error # Source type lacks default constructor
+dotnet_diagnostic.NUnit1017.severity = error # Specified source is not static
+dotnet_diagnostic.NUnit1018.severity = error # TestCaseSource param count mismatch (target method)
+dotnet_diagnostic.NUnit1019.severity = error # Source does not return I(Async)Enumerable
+dotnet_diagnostic.NUnit1020.severity = error # Parameters provided to field/property source
+dotnet_diagnostic.NUnit1021.severity = error # ValueSource should use nameof
+dotnet_diagnostic.NUnit1022.severity = error # Specified ValueSource is not static
+dotnet_diagnostic.NUnit1023.severity = error # ValueSource cannot supply required parameters
+dotnet_diagnostic.NUnit1024.severity = error # ValueSource does not return I(Async)Enumerable
+dotnet_diagnostic.NUnit1025.severity = error # ValueSource member does not exist
+dotnet_diagnostic.NUnit1026.severity = error # Test or setup/teardown method is not public
+dotnet_diagnostic.NUnit1027.severity = error # Test method has parameters but no arguments supplied
+dotnet_diagnostic.NUnit1028.severity = error # Non-test method is public
+dotnet_diagnostic.NUnit1029.severity = error # TestCaseSource param count mismatch (Test method)
+dotnet_diagnostic.NUnit1030.severity = error # TestCaseSource parameter type mismatch (Test method)
+dotnet_diagnostic.NUnit1031.severity = error # ValuesAttribute args must match parameter types
+dotnet_diagnostic.NUnit1032.severity = error # IDisposable field/property should be disposed in TearDown
+dotnet_diagnostic.NUnit1033.severity = error # TestContext.Write methods will be obsolete
+dotnet_diagnostic.NUnit1034.severity = error # Base TestFixtures should be abstract
+dotnet_diagnostic.NUnit1035.severity = error # Range 'step' parameter cannot be zero
+dotnet_diagnostic.NUnit1036.severity = error # Range: from < to when step is positive
+dotnet_diagnostic.NUnit1037.severity = error # Range: from > to when step is negative
+dotnet_diagnostic.NUnit1038.severity = error # Attribute values' types must match parameter type
+
+# Assertion Rules (NUnit2001 - )
+dotnet_diagnostic.NUnit2001.severity = error # Prefer Assert.That(..., Is.False) over ClassicAssert.False
+dotnet_diagnostic.NUnit2002.severity = error # Prefer Assert.That(..., Is.False) over ClassicAssert.IsFalse
+dotnet_diagnostic.NUnit2003.severity = error # Prefer Assert.That(..., Is.True) over ClassicAssert.IsTrue
+dotnet_diagnostic.NUnit2004.severity = error # Prefer Assert.That(..., Is.True) over ClassicAssert.True
+dotnet_diagnostic.NUnit2005.severity = error # Prefer Is.EqualTo over AreEqual
+dotnet_diagnostic.NUnit2006.severity = error # Prefer Is.Not.EqualTo over AreNotEqual
+dotnet_diagnostic.NUnit2007.severity = error # Actual value should not be a constant
+dotnet_diagnostic.NUnit2008.severity = error # Incorrect IgnoreCase usage
+dotnet_diagnostic.NUnit2009.severity = error # Same value used for actual and expected
+dotnet_diagnostic.NUnit2010.severity = error # Use EqualConstraint for better messages
+dotnet_diagnostic.NUnit2011.severity = error # Use ContainsConstraint for better messages
+dotnet_diagnostic.NUnit2012.severity = error # Use StartsWithConstraint for better messages
+dotnet_diagnostic.NUnit2013.severity = error # Use EndsWithConstraint for better messages
+dotnet_diagnostic.NUnit2014.severity = error # Use SomeItemsConstraint for better messages
+dotnet_diagnostic.NUnit2015.severity = error # Prefer Is.SameAs over AreSame
+dotnet_diagnostic.NUnit2016.severity = error # Prefer Is.Null over ClassicAssert.Null
+dotnet_diagnostic.NUnit2017.severity = error # Prefer Is.Null over ClassicAssert.IsNull
+dotnet_diagnostic.NUnit2018.severity = error # Prefer Is.Not.Null over ClassicAssert.NotNull
+dotnet_diagnostic.NUnit2019.severity = error # Prefer Is.Not.Null over ClassicAssert.IsNotNull
+dotnet_diagnostic.NUnit2020.severity = error # Incompatible types for SameAs constraint
+dotnet_diagnostic.NUnit2021.severity = error # Incompatible types for EqualTo constraint
+dotnet_diagnostic.NUnit2022.severity = error # Missing property required for constraint
+dotnet_diagnostic.NUnit2023.severity = error # Invalid NullConstraint usage
+dotnet_diagnostic.NUnit2024.severity = error # Wrong actual type with String constraint
+dotnet_diagnostic.NUnit2025.severity = error # Wrong actual type with ContainsConstraint
+dotnet_diagnostic.NUnit2026.severity = error # Wrong actual type with SomeItems+EqualConstraint
+dotnet_diagnostic.NUnit2027.severity = error # Prefer Is.GreaterThan over ClassicAssert.Greater
+dotnet_diagnostic.NUnit2028.severity = error # Prefer Is.GreaterThanOrEqualTo over GreaterOrEqual
+dotnet_diagnostic.NUnit2029.severity = error # Prefer Is.LessThan over ClassicAssert.Less
+dotnet_diagnostic.NUnit2030.severity = error # Prefer Is.LessThanOrEqualTo over LessOrEqual
+dotnet_diagnostic.NUnit2031.severity = error # Prefer Is.Not.SameAs over AreNotSame
+dotnet_diagnostic.NUnit2032.severity = error # Prefer Is.Zero over ClassicAssert.Zero
+dotnet_diagnostic.NUnit2033.severity = error # Prefer Is.Not.Zero over ClassicAssert.NotZero
+dotnet_diagnostic.NUnit2034.severity = error # Prefer Is.NaN over ClassicAssert.IsNaN
+dotnet_diagnostic.NUnit2035.severity = error # Prefer Is.Empty over ClassicAssert.IsEmpty
+dotnet_diagnostic.NUnit2036.severity = error # Prefer Is.Not.Empty over ClassicAssert.IsNotEmpty
+dotnet_diagnostic.NUnit2037.severity = error # Prefer Does.Contain over ClassicAssert.Contains
+dotnet_diagnostic.NUnit2038.severity = error # Prefer Is.InstanceOf over ClassicAssert.IsInstanceOf
+dotnet_diagnostic.NUnit2039.severity = error # Prefer Is.Not.InstanceOf over ClassicAssert.IsNotInstanceOf
+dotnet_diagnostic.NUnit2040.severity = error # Non-reference types for SameAs constraint
+dotnet_diagnostic.NUnit2041.severity = error # Incompatible types for comparison constraint
+dotnet_diagnostic.NUnit2042.severity = error # Comparison constraint on object
+dotnet_diagnostic.NUnit2043.severity = error # Use ComparisonConstraint for better messages
+dotnet_diagnostic.NUnit2044.severity = error # Non-delegate actual parameter
+dotnet_diagnostic.NUnit2045.severity = error # Use Assert.EnterMultipleScope or Assert.Multiple
+dotnet_diagnostic.NUnit2046.severity = error # Use CollectionConstraint for better messages
+dotnet_diagnostic.NUnit2047.severity = error # Incompatible types for Within constraint
+dotnet_diagnostic.NUnit2048.severity = error # Prefer Assert.That over StringAssert
+dotnet_diagnostic.NUnit2049.severity = error # Prefer Assert.That over CollectionAssert
+dotnet_diagnostic.NUnit2050.severity = error # NUnit 4 no longer supports string.Format spec
+dotnet_diagnostic.NUnit2051.severity = error # Prefer Is.Positive over ClassicAssert.Positive
+dotnet_diagnostic.NUnit2052.severity = error # Prefer Is.Negative over ClassicAssert.Negative
+dotnet_diagnostic.NUnit2053.severity = error # Prefer Is.AssignableFrom over ClassicAssert.IsAssignableFrom
+dotnet_diagnostic.NUnit2054.severity = error # Prefer Is.Not.AssignableFrom over ClassicAssert.IsNotAssignableFrom
+dotnet_diagnostic.NUnit2055.severity = error # Prefer Is.InstanceOf<T> over 'is T' expression
+dotnet_diagnostic.NUnit2056.severity = error # Prefer Assert.EnterMultipleScope statement over Multiple
+
+# Suppressor Rules (NUnit3001 - )
+dotnet_diagnostic.NUnit3001.severity = error # Expression checked in NotNull/IsNotNull/Assert.That
+dotnet_diagnostic.NUnit3002.severity = error # Field/Property initialized in SetUp/OneTimeSetUp
+dotnet_diagnostic.NUnit3003.severity = error # TestFixture instantiated via reflection
+dotnet_diagnostic.NUnit3004.severity = error # Field should be disposed in TearDown/OneTimeTearDown
+
+# Style Rules (NUnit4001 - )
+dotnet_diagnostic.NUnit4001.severity = error # Simplify the Values attribute
+dotnet_diagnostic.NUnit4002.severity = error # Use Specific constraint
+
 # C++ Files
 [*.{cpp,h,in}]
 curly_bracket_next_line = true
@@ -529,4 +642,4 @@ end_of_line = lf
 [*.{cmd, bat}]
 end_of_line = crlf
 
-vsspell_dictionary_languages = en-US
+vsspell_dictionary_languages = en-US

src/ReactiveUI.Splat.Tests/TestConfiguration.cs renamed to integrationtests/IntegrationTests.Shared.Tests/AssemblyInfo.Parallel.cs

@@ -1,8 +1,9 @@
-// Copyright (c) 2025 .NET Foundation and Contributors. All rights reserved.
+// 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 Xunit;
+using NUnit.Framework;
 
-[assembly: CollectionBehavior(DisableTestParallelization = true, MaxParallelThreads = 1)]
+[assembly: Parallelizable(ParallelScope.Fixtures)]
+[assembly: LevelOfParallelism(4)]

integrationtests/IntegrationTests.Shared.Tests/Features/Login/LoginViewModelTests.cs

@@ -12,26 +12,25 @@
 
 using DynamicData;
 
-using FluentAssertions;
-
 using Microsoft.Reactive.Testing;
 
 using ReactiveUI;
 using ReactiveUI.Testing;
 
-using Xunit;
+using NUnit.Framework;
 
 namespace IntegrationTests.Shared.Tests.Features.Login
 {
     /// <summary>
     /// Tests associated with the LoginViewModel class.
     /// </summary>
+    [TestFixture]
     public class LoginViewModelTests
     {
         /// <summary>
         /// Checks to make sure that the cancel command actually cancels a login attempt.
         /// </summary>
-        [Fact]
+        [Test]
         public void CancelButton_Cancels_Login()
         {
             var scheduler = new TestScheduler();
@@ -43,13 +42,13 @@ public void CancelButton_Cancels_Login()
 
             scheduler.AdvanceByMs(TimeSpan.FromSeconds(1).Milliseconds);
 
-            sut.Login.Subscribe(x => x.Should().Be(true));
+            sut.Login.Subscribe(x => Assert.That(x, Is.EqualTo(true)));
 
             Observable
                 .Return(Unit.Default)
                 .InvokeCommand(sut.Login);
 
-            sut.Cancel.CanExecute.Subscribe(x => x.Should().Be(true));
+            sut.Cancel.CanExecute.Subscribe(x => Assert.That(x, Is.EqualTo(true)));
 
             scheduler.AdvanceByMs(1000);
 
@@ -61,7 +60,7 @@ public void CancelButton_Cancels_Login()
         /// <summary>
         /// Checks to make sure that the cancel button is available within two seconds.
         /// </summary>
-        [Fact]
+        [Test]
         public void CancelButton_IsAvailableUntil_TwoSeconds()
         {
             var actual = false;
@@ -79,40 +78,40 @@ public void CancelButton_IsAvailableUntil_TwoSeconds()
 
             Observable.Return(Unit.Default).InvokeCommand(sut.Login);
 
-            actual.Should().Be(false);
+            Assert.That(actual, Is.EqualTo(false));
 
             // 50ms
             scheduler.AdvanceByMs(50);
 
-            actual.Should().Be(true);
+            Assert.That(actual, Is.EqualTo(true));
 
             // 1sec 50ms
             scheduler.AdvanceByMs(TimeSpan.FromSeconds(1).TotalMilliseconds);
 
-            actual.Should().Be(true);
+            Assert.That(actual, Is.EqualTo(true));
 
             // 2sec 50sms
             scheduler.AdvanceByMs(TimeSpan.FromSeconds(1).TotalMilliseconds);
 
-            actual.Should().Be(false);
+            Assert.That(actual, Is.EqualTo(false));
         }
 
         /// <summary>
         /// Checks to make sure that the login button is disabled when not logging in.
         /// </summary>
         /// <returns>A task to monitor the progress.</returns>
-        [Fact]
+        [Test]
         public async Task CancelButton_IsDisabled_WhenNot_LoggingIn()
         {
             LoginViewModel sut = new LoginViewModelBuilder();
 
-            (await sut.Cancel.CanExecute.FirstAsync()).Should().Be(false);
+            Assert.That((await sut.Cancel.CanExecute.FirstAsync()), Is.EqualTo(false));
         }
 
         /// <summary>
         /// Checks to make sure that the login ticks correctly and the action is performed.
         /// </summary>
-        [Fact]
+        [Test]
         public void CanLogin_TicksCorrectly()
         {
             var scheduler = new TestScheduler();
@@ -127,20 +126,20 @@ public void CanLogin_TicksCorrectly()
 
             scheduler.AdvanceByMs(TimeSpan.FromSeconds(5).TotalMilliseconds);
 
-            collection.ToList().Should().BeEquivalentTo(new[] { false, true, false });
+            Assert.That(collection.ToList(), Is.EqualTo(new[] { false, true, false }));
         }
 
         /// <summary>
         /// Checks to make sure that the login button is disabled with default values.
         /// </summary>
         /// <returns>A task to monitor the progress.</returns>
-        [Fact]
+        [Test]
         public async Task LoginButton_IsDisabled_ByDefault()
         {
             LoginViewModel sut = new LoginViewModelBuilder();
 
             var result = await sut.Login.CanExecute.FirstAsync();
-            result.Should().Be(false);
+            Assert.That(result, Is.EqualTo(false));
         }
 
         /// <summary>
@@ -162,7 +161,7 @@ public async Task LoginButton_IsDisabled_WhenUserNameOrPassword_IsEmpty(string u
                 .WithUserName(userName)
                 .WithPassword(password);
 
-            (await sut.Login.CanExecute.FirstAsync()).Should().Be(false);
+            Assert.That((await sut.Login.CanExecute.FirstAsync()), Is.EqualTo(false));
         }
 
         /// <summary>
@@ -179,13 +178,13 @@ public async Task LoginButton_IsEnabled_WhenUserNameAndPassword_IsNotEmptyAsync(
                 .WithUserName(userName)
                 .WithPassword(password);
 
-            (await sut.Login.CanExecute.FirstAsync()).Should().Be(true);
+            Assert.That((await sut.Login.CanExecute.FirstAsync()), Is.EqualTo(true));
         }
 
         /// <summary>
         /// Checks to make sure the user can login with a correct password.
         /// </summary>
-        [Fact]
+        [Test]
         public void User_CanLogin_WithCorrect_Password()
         {
             var scheduler = new TestScheduler();
@@ -201,13 +200,13 @@ public void User_CanLogin_WithCorrect_Password()
 
             scheduler.AdvanceByMs(TimeSpan.FromSeconds(3).TotalMilliseconds);
 
-            value.Should().Be(true);
+            Assert.That(value, Is.EqualTo(true));
         }
 
         /// <summary>
         /// Checks to make sure the user cannot login with a incorrect password.
         /// </summary>
-        [Fact]
+        [Test]
         public void User_CannotLogin_WithIncorrect_Password()
         {
             var scheduler = new TestScheduler();
@@ -223,7 +222,7 @@ public void User_CannotLogin_WithIncorrect_Password()
 
             scheduler.AdvanceByMs(TimeSpan.FromSeconds(3).TotalMilliseconds);
 
-            value.Should().Be(false);
+            Assert.That(value, Is.EqualTo(false));
         }
     }
 }

integrationtests/IntegrationTests.Shared.Tests/IntegrationTests.Shared.Tests.csproj

@@ -9,17 +9,11 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
-    <PackageReference Include="xunit" Version="2.9.3" />
-    <PackageReference Include="xunit.runner.console" Version="2.9.3">
+    <PackageReference Include="NUnit" Version="4.4.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="5.*">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4">
-      <PrivateAssets>all</PrivateAssets>
-      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
-    </PackageReference>
-    <PackageReference Include="Xunit.StaFact" Version="1.2.69" />
-    <PackageReference Include="FluentAssertions" Version="8.6.0" />
   </ItemGroup>
 
   <ItemGroup>

src/Directory.Build.props

@@ -45,16 +45,14 @@
     <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
   </PropertyGroup>
   <ItemGroup Condition="$(IsTestProject)">
+    <PackageReference Include="NUnit" />
+    <PackageReference Include="NUnit3TestAdapter" />
+    <PackageReference Include="NUnit.Analyzers" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
-    <PackageReference Include="xunit" />
-    <PackageReference Include="xunit.runner.console" />
-    <PackageReference Include="xunit.runner.visualstudio" />
-    <PackageReference Include="Xunit.StaFact" />
-    <PackageReference Include="FluentAssertions" />
     <PackageReference Include="Microsoft.Reactive.Testing" />
     <PackageReference Include="PublicApiGenerator" />
     <PackageReference Include="coverlet.msbuild" PrivateAssets="All" />
-    <PackageReference Include="Verify.Xunit" />
+    <PackageReference Include="Verify.NUnit" />
   </ItemGroup>
   <ItemGroup Condition="'$(IsTestProject)' != 'true'">
     <PackageReference Include="Microsoft.SourceLink.GitHub" PrivateAssets="All" />

src/Directory.Packages.props

@@ -11,11 +11,13 @@
   <ItemGroup>
     <PackageVersion Include="coverlet.msbuild" Version="6.0.4" />
     <PackageVersion Include="DynamicData" Version="9.4.1" />
-    <PackageVersion Include="FluentAssertions" Version="8.6.0" />
     <PackageVersion Include="JetBrains.DotMemoryUnit" Version="3.2.20220510" />
     <PackageVersion Include="Microsoft.CodeAnalysis.Analyzers" Version="3.11.0" />
     <PackageVersion Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.14.0" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageVersion Include="NUnit" Version="4.4.0" />
+    <PackageVersion Include="NUnit3TestAdapter" Version="5.1.0" />
+    <PackageVersion Include="NUnit.Analyzers" Version="4.10.0" />
     <PackageVersion Include="Microsoft.Reactive.Testing" Version="6.0.2" />
     <PackageVersion Include="System.Reactive" Version="6.0.2" />
     <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="8.0.0" />
@@ -36,11 +38,7 @@
     <PackageVersion Include="System.IO.FileSystem.Primitives" Version="4.3.0" />
     <PackageVersion Include="System.Runtime.Serialization.Primitives" Version="4.3.0" />
     <PackageVersion Include="System.Text.Json" Version="9.0.8" />
-    <PackageVersion Include="Verify.Xunit" Version="30.7.3" />
-    <PackageVersion Include="xunit" Version="2.9.3" />
-    <PackageVersion Include="xunit.runner.console" Version="2.9.3" />
-    <PackageVersion Include="xunit.runner.visualstudio" Version="3.1.4" />
-    <PackageVersion Include="Xunit.StaFact" Version="1.2.69" />
+    <PackageVersion Include="Verify.NUnit" Version="30.7.3" />
     <PackageVersion Include="Xamarin.AndroidX.Core" Version="$(XamarinAndroidXCoreVersion)" />
     <PackageVersion Include="Xamarin.AndroidX.Preference" Version="1.2.1.9" />
     <PackageVersion Include="Xamarin.AndroidX.Legacy.Support.Core.UI" Version="1.0.0.29" />