Infra: Migrate test framework from xUnit to NUnit (modeled after puppeteer-sharp)

[kblok]

Description

Migrate PlaywrightSharp.Tests from xUnit to NUnit 4.x, following the same patterns used in puppeteer-sharp. This is a large structural change that touches every test file.

What to Implement

1. Update package references

In PlaywrightSharp.Tests.csproj:

• Remove: xunit, xunit.runner.visualstudio, MicrosoftExtensions.Logging.Xunit
• Add: NUnit (4.1.0+), NUnit3TestAdapter (4.6.0+), NUnit.Analyzers (4.3.0+)
• Keep: Microsoft.NET.Test.Sdk

2. Create PlaywrightSharp.Nunit project

New project mirroring puppeteer-sharp's PuppeteerSharp.Nunit:

• PlaywrightTestAttribute — custom test attribute that:
  • Maps upstream test file + test name for traceability
  • Reads PRODUCT env var (CHROMIUM/FIREFOX/WEBKIT)
  • Reads HEADLESS env var
  • Loads test expectations from embedded JSON files for platform-specific skip/fail management
• Test expectation JSON files (TestExpectations.upstream.json, TestExpectations.local.json)

3. Rewrite test base classes

Replace xUnit IAsyncLifetime + ICollectionFixture pattern with NUnit equivalents:

xUnit	NUnit
IAsyncLifetime.InitializeAsync	[SetUp] async Task
IAsyncLifetime.DisposeAsync	[TearDown] async Task
ICollectionFixture<T>	[SetUpFixture] with [OneTimeSetUp]/[OneTimeTearDown]
[Collection("name")]	Namespace-based fixture scoping
[Fact] / [Retry]	[Test] / [PlaywrightTest]
[Trait("Category", "chromium")]	[Category("chromium")]
ITestOutputHelper	TestContext.Out

New base class hierarchy:

• PlaywrightSharpBaseTest — [SetUp]: workspace, server reset. Provides Server, HttpsServer
• PlaywrightSharpBrowserBaseTest — [SetUp]: launch browser. [TearDown]: dispose. Provides Browser
• PlaywrightSharpBrowserContextBaseTest — [SetUp]: new context. Provides Context
• PlaywrightSharpPageBaseTest — [SetUp]: new page. [TearDown]: close page. Provides Page

4. Create SetUpFixture for global setup

Replace PlaywrightSharpLoader and collection fixtures:

[SetUpFixture]
public class TestServerSetup
{
    [OneTimeSetUp]
    public async Task GlobalSetup()
    {
        // Download browsers
        // Start HTTP/HTTPS servers
    }

    [OneTimeTearDown]
    public async Task GlobalTeardown()
    {
        // Stop servers
    }
}

5. Migrate all test files (~176 files)

For each test file:

• Remove [Collection(...)] attribute
• Replace [Trait("Category", "chromium")] → [Category("chromium")]
• Replace [Retry] / [Fact] → [Test, PlaywrightTest("file.spec", "test name")]
• Replace constructor (ITestOutputHelper output) : base(output) → parameterless constructor
• Replace Assert.Equal(a, b) → Assert.That(b, Is.EqualTo(a))
• Replace Assert.True(x) → Assert.That(x, Is.True)
• Replace Assert.Contains(x, col) → Assert.That(col, Does.Contain(x))
• Replace Assert.Throws<T> → Assert.ThrowsAsync<T> or Assert.That(() => ..., Throws.TypeOf<T>())

6. Remove custom xUnit framework

Delete:

• PlaywrightXunitTestFramework.cs
• PlaywrightXunitTestFrameworkExecutor.cs
• PlaywrightXunitTestAssemblyRunner.cs
• RetryAttribute.cs, RetryFactDiscoverer.cs, RetryTestCase.cs
• DelayedMessageBus.cs
• Collection definition files

7. Configure test parallelization

• NUnit default is parallel; add [assembly: NonParallelizable] or configure in .runsettings to match current sequential execution behavior
• Consider [Parallelizable(ParallelScope.None)] on base class

Upstream References

• puppeteer-sharp lib/PuppeteerSharp.Tests/ (NUnit test patterns)
• puppeteer-sharp lib/PuppeteerSharp.Nunit/ (custom attribute infrastructure)
• puppeteer-sharp lib/PuppeteerSharp.Tests/PuppeteerBaseTest.cs (base class hierarchy)
• puppeteer-sharp lib/PuppeteerSharp.Tests/TestServerSetup.cs (global setup fixture)

Files to Create

• src/PlaywrightSharp.Nunit/PlaywrightSharp.Nunit.csproj (new project)
• src/PlaywrightSharp.Nunit/PlaywrightTestAttribute.cs
• src/PlaywrightSharp.Nunit/TestExpectations/ (expectation JSONs)

Files to Modify

• src/PlaywrightSharp.Tests/PlaywrightSharp.Tests.csproj
• src/PlaywrightSharp.Tests/BaseTests/PlaywrightSharpBaseTest.cs
• src/PlaywrightSharp.Tests/BaseTests/PlaywrightSharpBrowserBaseTest.cs
• src/PlaywrightSharp.Tests/BaseTests/PlaywrightSharpPageBaseTest.cs
• All ~176 test files in src/PlaywrightSharp.Tests/
• src/PlaywrightSharp.sln (add new project)

Files to Delete

• Custom xUnit framework files (RetryAttribute, DelayedMessageBus, etc.)
• Collection definition files

Verification

dotnet build ./src/PlaywrightSharp.sln
dotnet test ./src/PlaywrightSharp.Tests/PlaywrightSharp.Tests.csproj --filter Category=chromium -c Debug -f net10.0
PRODUCT=FIREFOX dotnet test ./src/PlaywrightSharp.Tests/PlaywrightSharp.Tests.csproj --filter Category=firefox -c Debug -f net10.0

Dependencies

Depends on: #1

[kblok]

Implemented in PR #73

[kblok]

Implemented in PR #74