aspnetcore/test/Templates.Test/Infrastructure/CaptureSeleniumLogsAttribute.cs

using OpenQA.Selenium;
using System;
using System.Linq;
using System.Reflection;
using Xunit.Sdk;

namespace Templates.Test.Infrastructure
{
    // This has to use BeforeAfterTestAttribute because running the log capture
    // in the BrowserFixture.Dispose method is too late, and we can't add logging
    // to the test.
    public class CaptureSeleniumLogsAttribute : BeforeAfterTestAttribute
    {
        public override void Before(MethodInfo methodUnderTest)
        {
            if (!typeof(BrowserTestBase).IsAssignableFrom(methodUnderTest.DeclaringType))
            {
                throw new InvalidOperationException("This should only be used with BrowserTestBase");
            }
        }

        public override void After(MethodInfo methodUnderTest)
        {
            var browser = BrowserTestBase.Browser;
            var logs = BrowserTestBase.Logs;
            var output = BrowserTestBase.Output;

            if(logs != null && output != null)
            {
                // Put browser logs first, the test UI will truncate output after a certain length
                // and the browser logs will include exceptions thrown by js in the browser.
                foreach (var kind in logs.AvailableLogTypes.OrderBy(k => k == LogType.Browser ? 0 : 1))
                {
                    output.WriteLine($"{kind} Logs from Selenium:");

                    var entries = logs.GetLog(kind);
                    foreach (LogEntry entry in entries)
                    {
                        output.WriteLine($"[{entry.Timestamp}] - {entry.Level} - {entry.Message}");
                    }

                    output.WriteLine("");
                    output.WriteLine("");
                }
            }
        }
    }
}