LoggingTestWithInjectedFactory.cs

using System.Threading.Tasks;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc.Testing;
using Microsoft.Extensions.Logging;
using Xunit;

namespace SampleWebApplicationSerilog.Tests
{
    public class LoggingTestWithInjectedFactory : IClassFixture<CustomWebApplicationFactory<Startup>>
    {
        private readonly CustomWebApplicationFactory<Startup> _factory;

        public LoggingTestWithInjectedFactory(CustomWebApplicationFactory<Startup> factory)
        {
            _factory = factory;
            // In this case, the factory will be reused for all tests, so the sink will be shared as well.
            // We can clear the sink before each test execution, as xUnit will not run this tests in parallel.
            _factory.GetTestLoggerSink().Clear();
            // When running on 2.x, the server is not initialized until it is explicitly started or the first client is created.
            // So we need to use:
            // if (_factory.TryGetTestLoggerSink(out var testLoggerSink)) testLoggerSink.Clear();
        }

        [Fact]
        public async Task ShouldLogHelloWorld()
        {
            // Arrange

            // Act
            await _factory.CreateDefaultClient().GetAsync("/");

            // Assert
            var log = Assert.Single(_factory.GetTestLoggerSink().LogEntries);
            // Assert the message rendered by a default formatter
            Assert.Equal("Hello World!", log.Message);
        }

        [Fact]
        public async Task ShouldUseScope()
        {
            // Arrange

            // Act
            await _factory.CreateDefaultClient().GetAsync("/");

            // Assert
            var log = Assert.Single(_factory.GetTestLoggerSink().LogEntries);
            var scope = Assert.Single(log.Scopes);
            // Assert the scope rendered by a default formatter
            Assert.Equal("I'm in the GET scope", scope.Message);
        }

        [Fact]
        public async Task ShouldBeginScope()
        {
            // Arrange

            // Act
            await _factory.CreateDefaultClient().GetAsync("/");

            // Assert
            var scope = Assert.Single(_factory.GetTestLoggerSink().Scopes);
            // Assert the scope rendered by a default formatter
            Assert.Equal("I'm in the GET scope", scope.Message);
        }
    }

    public class CustomWebApplicationFactory<TStartup> : WebApplicationFactory<TStartup>
         where TStartup : class
    {
        protected override void ConfigureWebHost(IWebHostBuilder builder)
        {
            builder.UseTestLogging(options => options.FilterByNamespace(nameof(SampleWebApplicationSerilog)));
        }
    }
}