Serilog and WebApplicationFactory

I have a .NET Core 2.1 project. I’m running tests using the new WebApplicationFactory. This uses information in the program.cs to bootstrap things.

When running tests, I wan’t to mock the ILogger infrastructure, not use the Serilog implementation. From what I can tell, it’s not trivial to remove the Serilog implementation from DI.

Serilog is set up in program.cs like this:

  public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .UseSerilog((context, configureLogger) =>
                {
                       // configuration omitted. 
                });

This is a cut down version of my Testing contex

 public class TestingContext : WebApplicationFactory<Startup>
    {
        /// <summary>
        /// Mocked ILogger
        /// </summary>
        public Mock<ILogger> Logger { get; } = new Mock<ILogger>();

        protected override void ConfigureWebHost(IWebHostBuilder builder)
        {
            var loggerProvider = new Mock<ILoggerProvider>();
            loggerProvider.Setup(x => x.CreateLogger(It.IsAny<string>())).Returns(Logger.Object);

            builder
                .UseDefaultServiceProvider(p => p.ValidateScopes = true)
                .ConfigureLogging(l =>
                {
                    // this is the only way I have found to remove Serilog
                    var serilog = (from s in l.Services
                        where s.ImplementationFactory != null &&
                              s.ImplementationFactory.Target.GetType().Assembly.FullName.Contains("Serilog.AspNetCore")
                        select s).FirstOrDefault();

                    if (serilog != null)
                    {
                        l.Services.Remove(serilog);
                    }

                    // this does not clear Serilog, it removes all ILoggerProvider
                    // Serilog is registered as an ILoggerFactory
                    l.ClearProviders(); 
                    l.AddProvider(loggerProvider.Object);
                });
        }
    }

[kimbell]

One of the first statements from that repos read me file is:

ASP.NET Core 2.0+ Instructions ASP.NET Core 2.0 applications should prefer Serilog.AspNetCore and UseSerilog() instead.

The AspNetCore package replaces the default LoggerFactory registered by Microsoft. Looking at the SerilogLoggerFactory, it’s using a SerilogLoggerProvider that is of type ILoggerProvider.

Since one has gone through the effort of creating a new LoggerFactory, I’m assuming there is a reason for this. I’m curious as to why? What does it bring to the table that isn’t possible by just adding Serilog as another provider?

[nblumhardt]

@kimbell ClearProviders() removes providers from the default logger factory; since Serilog replaces the default logger factory, there’s no way ClearProviders() can have this effect. Thanks for the feedback, though - good to have this here for others who need the same info 👍