[Feature]: Load Playwright settings programmatically as an alternative to a `.runsettings` file

🚀 Feature Request

Currently, setting the BrowserTypeLaunchOptions when running tests with the Microsoft.Playwright.MSTest, Microsoft.Playwright.NUnit or Microsoft.Playwright.Xunit pacakge is controlled through the .runsettings configuration file.

It would be nice to be able to control the launch options programmatically, just like BrowserNewContextOptions can be controlled programmatically by overriding the ContextOptions() method.

Example

using System;
using System.Threading.Tasks;
using Microsoft.Playwright;
using Microsoft.Playwright.TestAdapter;
using Microsoft.Playwright.Xunit;
using Xunit;

public class IntegrationTests(WebAppFixture webAppFixture) : PageTest, IClassFixture<WebAppFixture>
{
    // 👇 Proposed new virtual method where browser, launch options and more can be controlled programmatically
    protected override PlaywrightSettings PlaywrightSettings()
    {
        return new PlaywrightSettings
        {
            Browser = PlaywrightBrowser.Firefox,
            LaunchOptions = new BrowserTypeLaunchOptions
            {
                Headless = false,
                SlowMo = 100,
                Timeout = 20_000,
            },
            ExpectTimeout = TimeSpan.FromSeconds(10),
        };
    }

    [Fact]
    public async Task TestSearchPage()
    {
        await Page.GotoAsync(webAppFixture.Url("search"));
        await Expect(Page).ToHaveTitleAsync("Search");
    }
}

This example is given with Xunit but would work the same with MSTest or NUnit.

Motivation

Controlling options programatically opens up new possibilities that are not achievable with a .runsettings file. For example, one could decide to run tests on Firefox based on some runtime conditions or change the value of the Timeout based on what hardware the tests are running on. This would give a lot of power to Playwright users.

Also, having a new PlaywrightSettings type is great for discoverability. Typing properties with autocompletion support from your IDE is a much better experience than writing XML elements in a .runsettings file without any autocompletion.

Finally, .runsettings support in Rider is pretty broken, I was not able to get the Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.ISettingsProvider.Load method to be called, rendring Playwright .runsettings unusable with Rider. See also TestCaseFilter in .runsettings ignored.

Review the Microsoft.Playwright.MSTest, Microsoft.Playwright.NUnit, and Microsoft.Playwright.Xunit integrations, along with the existing .runsettings configuration and ContextOptions() handling. Compare how browser launch and test settings are currently supplied, then define equivalent programmatic behavior across all three runners and verify that the proposed PlaywrightSettings API covers the requested options.