Migrate test projects from xUnit to NUnit 4.4.0

[Copilot]

Migration plan for xUnit to NUnit 4.4.0:

• Setup prerequisites (install .NET 8/9/10, unshallow repo, restore workloads)
• Verify current tests pass with xUnit
• Update Directory.Packages.props to replace xUnit/FluentAssertions with NUnit packages
• Update test project .csproj to reference NUnit packages
• Create AssemblyInfo.Parallel.cs for parallelization configuration
• Create tests.runsettings file for CI configuration
• Convert DisposableExtensionsTests.cs from xUnit to NUnit
• Convert ReactiveExtensionsTests.cs from xUnit to NUnit
• Build and verify all tests pass with NUnit (10/10 tests passing)
• Fix NUnit analyzer errors (NUnit4002)
• Run final code review and security checks

Summary

Successfully migrated all test projects from xUnit + FluentAssertions to NUnit 4.4.0 with NUnit.Analyzers enabled.

Latest Changes:

Fixed NUnit analyzer errors (NUnit4002) by replacing Assert.That(result, Is.EqualTo(0)) with Assert.That(result, Is.Zero) in 4 test methods. This follows NUnit best practices for comparing numeric values to zero.

Verification:

• ✅ All 10 tests passing
• ✅ Clean build with no warnings or errors
• ✅ NUnit.Analyzers enabled and no violations
• ✅ Tests work with both default settings and runsettings file

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Migrate xUnit to nUnit</issue_title>
<issue_description># Migrate xUnit + FluentAssertions to NUnit 4.4.0 with Controlled Concurrency

Prereq steps that must be done for you to be able to compile (see copilot-instructions.md in the .github folder for further details)
1, Install .net 8/9/10 via the install script.
2. unshallow the commits
3. dotnet workload restore in the /src folder

Goal: Convert all test projects from xUnit to NUnit 4.4.0, remove FluentAssertions, use Assert.That style, and configure per-class sequential execution with controlled parallelism across classes for ReactiveUI's static-heavy codebase. If using the static classes inside ReactiveUI, only sequential access to ensure the tests run, otherwise parallelise.

1. Update Test Project Packages

Remove

• xunit
• xunit.runner.visualstudio
• FluentAssertions

Add

• NUnit (4.4.0)
• NUnit3TestAdapter (latest stable, e.g., 5.2.0)
• Microsoft.NET.Test.Sdk (latest stable, e.g., 18.0.1 )

Updated .csproj Example:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <IsPackable>false</IsPackable>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="NUnit" Version="4.4.0" />
    <PackageReference Include="NUnit3TestAdapter" Version="5.2.0" />
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
  </ItemGroup>
</Project>

2. Configure Concurrency for Static Classes

To prevent concurrency issues with ReactiveUI's static classes, run tests sequentially within each test fixture (class) but allow parallelism across fixtures.

2.1 Assembly-Level Concurrency

Add an AssemblyInfo.Parallel.cs file (outside any namespace) in each test project:

using NUnit.Framework;

[assembly: Parallelizable(ParallelScope.Fixtures)]
[assembly: LevelOfParallelism(4)]

• ParallelScope.Fixtures: Runs test fixtures in parallel, but tests within each fixture sequentially.
• LevelOfParallelism(4): Caps parallel workers (adjust based on CI resources, e.g., CPU count/2).

2.2 CI Runsettings

Create a tests.runsettings file at the repo root:

<RunSettings>
  <NUnit>
    <NumberOfTestWorkers>4</NumberOfTestWorkers>
  </NUnit>
</RunSettings>

Usage:

dotnet test --settings tests.runsettings

Override for full serialization (if static state is fragile):

dotnet test -- NUnit.NumberOfTestWorkers=1

3. xUnit to NUnit Attribute & API Mappings

xUnit	NUnit 4.4.0 Equivalent
[Fact]	[Test]
[Theory] + [InlineData(...)]	[TestCase(...)]
[Theory] + [MemberData]	[TestCaseSource(nameof(Data))]
[Theory] + [ClassData<T>]	[TestCaseSource(typeof(T))]
Assert.Equal(a,b)	Assert.That(b, Is.EqualTo(a))
Assert.NotEqual(a,b)	Assert.That(b, Is.Not.EqualTo(a))
Assert.True(expr)	Assert.That(expr, Is.True)
Assert.False(expr)	Assert.That(expr, Is.False)
Assert.Null(x)	Assert.That(x, Is.Null)
Assert.NotNull(x)	Assert.That(x, Is.Not.Null)
Assert.Throws<T>(...)	Assert.Throws<T>(...) or Assert.That(..., Throws.TypeOf<T>())
Assert.Collection/Contains	Assert.That(coll, Does.Contain(item))
Trait("Category","X")	[Category("X")]
IClassFixture<T>	[OneTimeSetUp]/[OneTimeTearDown] with shared state
[Collection("name")]	[NonParallelizable] on conflicting fixtures

NOTE: for multiple asserts use the IDisposable Assert.EnterMultipleScope method.

  using (Assert.EnterMultipleScope())
    {
        Assert.That(result.RealPart, Is.EqualTo(5.2));
        Assert.That(result.ImaginaryPart, Is.EqualTo(3.9));
    }

4. Remove FluentAssertions: Convert to Assert.That

Common Conversions:

FluentAssertions	NUnit 4.4.0 Equivalent
actual.Should().Be(expected)	Assert.That(actual, Is.EqualTo(expected))
actual.Should().NotBe(expected)	Assert.That(actual, Is.Not.EqualTo(expected))
flag.Should().BeTrue()	Assert.That(flag, Is.True)
value.Should().BeNull()	Assert.That(value, Is.Null)
str.Should().Contain("x")	Assert.That(str, Does.Contain("x"))
str.Should().StartWith("pre")	Assert.That(str, Does.StartWith("pre"))
n.Should().BeGreaterThan(5)	Assert.That(n, Is.GreaterThan(5))
n.Should().BeInRange(1,10)	Assert.That(n, Is.InRange(1,10))
items.Should().BeEmpty()	Assert.That(items, Is.Empty)
items.Should().BeEquivalentTo(new[] {1,2,3})	Assert.That(items, Is.EquivalentTo(new[] {1,2,3}))
act.Should().Throw<InvalidOperationException>()	Assert.That(act, Throws.TypeOf<InvalidOperationException>())
`await actAsync.Should().ThrowAsync<InvalidOperationExcept...

• Fixes Migrate xUnit to nUnit #98

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[glennawatson]

@copilot You're going to have to re-install all the .NET sdks, since it has a different path, so install 8/9/10

[Copilot]

@copilot You're going to have to re-install all the .NET sdks, since it has a different path, so install 8/9/10

Re-installed .NET 8, 9, and 10 SDKs to the system location (/usr/share/dotnet). All SDKs are now available, repository is unshallowed, workloads restored, and tests pass successfully.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• aka.ms
  • Triggering command: curl -I -sSL --retry 5 --retry-delay 2 --connect-timeout 15 REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[glennawatson]

@copilot Get the latest commit, do the normal prereq (install .NET 8/9/10 regardless if any is installed yet since its required due to the environment path changes, unshallow the commits, and dotnet workload restore). I've enabled nunit analyzers and there's a bunch of the tests failing now due to the analyzers. Determine the build errors and fix.

[Copilot]

@copilot Get the latest commit, do the normal prereq (install .NET 8/9/10 regardless if any is installed yet since its required due to the environment path changes, unshallow the commits, and dotnet w...

Completed all prerequisites and fixed NUnit analyzer errors:

1. ✅ Installed .NET 8, 9, and 10 SDKs to system location
2. ✅ Unshallowed repository
3. ✅ Restored workloads
4. ✅ Fixed 4 NUnit analyzer errors (NUnit4002) by replacing Is.EqualTo(0) with Is.Zero

All tests passing, build succeeds with no warnings or errors. Commit: 2316e93

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• aka.ms
  • Triggering command: curl -I -sSL --retry 5 --retry-delay 2 --connect-timeout 15 REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[codecov]

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[github-actions]

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