Htmx Extension methods for Playwright Testing

HtmxExtensions.cs

using Microsoft.Playwright;

namespace HtmxPlaywrightIntegration.Tests;

public static class HtmxExtensions
{
    private const string Continue = "playwright:continue";
    
    public static Task WaitForHtmx(this IPage page)
    {
        return page.WaitForConsoleMessageAsync(new() {
            Predicate = message => message.Text == Continue
        });
    }

    public static Task RegisterHtmxLifecycleListener(this IPage page)
    {
        return page.AddScriptTagAsync(new()
        {
            // language=javascript
            Content = $$"""
                      document.body.addEventListener('htmx:afterSettle', function(evt) {
                          console.log('{{Continue}}');
                      });
                      """
        });
    }
}

Tests.cs

namespace HtmxPlaywrightIntegration.Tests;

[Parallelizable(ParallelScope.Self)]
[TestFixture]
public class Tests : PageTest
{
    [Test]
    public async Task CanIncrementCountUsingHtmx()
    {
        await Page.GotoAsync("http://localhost:5170");

        await Page.RegisterHtmxLifecycleListener();

        // create a locator
        var button = Page.Locator("text=Increment");
        var body = Page.Locator("#value");

        var currentCount = int.Parse(await body.TextContentAsync() ?? "-1");

        // Click the get started link.
        await button.ClickAsync();
        await Page.WaitForHtmx();
        
        // Expects the URL to contain intro.
        await Expect(body).ToHaveTextAsync($"{currentCount+1}");
    }
}