Logging

This page describes functionality related to logging in tests.

• xUnit test logging
• In-memory test logging
• Serilog in-memory log sink
• Serilog xUnit log sink

Installation

The following functionality is available when installing this package:

PM> Install-Package -Name Arcus.Testing.Logging

xUnit Test Logging

The Arcus.Testing.Logging library provides a XunitTestLogger type that's an implementation of the abstracted Microsoft Ilogger inside the xUnit test framework.

Log messages written to the ILogger instance will be written to the xUnit test output.

using Arcus.Testing.Logging;
using Microsoft.Extensions.Logging;
using Xunit.Abstractions;

public class TestClass
{
    private readonly ILogger _testLogger;

    public TestClass(ITestOutputHelper outputWriter)
    {
        _testLogger = new XunitTestLogger(outputWriter);
    }
}

xUnit Test Logging in .NET Core

During integration testing of hosts, one could find the need to add the log messages to the xUnit output for defect localization. The Arcus.Testing.Logging library provides an extension to add this in a more dev-friendly way.

using Arcus.Testing.Logging;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Hosting;
using Xunit.Abstractions;

public class TestClass
{
    private readonly ILogger _outputWriter;

    public TestClass(ITestOutputHelper outputWriter)
    {
        _outputWriter = outputWriter;
    }

    [Fact]
    public void TestMethod()
    {
        IHost host = new HostBuilder()
            .ConfigureLogging(loggingBuilder => loggingBuilder.AddXunitTestLogging(_outputWriter))
            .Build();
    }
}

In-memory Test Logging

The Arcus.Testing.Logging library provides a InMemoryLogger and InMemoryLogger<T> which are Microsoft Logging ILogger and ILogger<T> implementations respectively. These types help in tracking logged messages and their metadata information like the level on which the message was logged or the related exception.

using Arcus.Testing.Logging;
using Microsoft.Extensions.Logging;

ILogger logger = new InMemoryLogger();

logger.LogInformation("This is an informational message");

// Either get the message directly, or
IEnumerable<string> messages = logger.Messages;

// Use the full `LogEntry` object to retrieve the message.
IEnumerable<LogEntry> entries = logger.Entries;
LogEntry entry = entries.First();

// Level = Information
LogLevel level = entry.Level;
// Message = "This is a informational message"
string message = entry.Message;

Or, alternatively you can use the generic variant:

using Arcus.Testing.Logging;
using Microsoft.Extensions.Logging;

ILogger<MyType> logger = new InMemoryLogger<MyType>();

logger.LogInformation("This is an informational message");

IEnumerable<string> messages = logger.Messages;

Serilog in-memory log sink

The Arcus.Testing.Logging library provides a InMemoryLogSink which is a Serilog log sink that collectes written log emits in-memory so the test infrastructure can assert on the actual rendered messages and possible properties available on the log emit.

using Arcus.Testing.Logging;
using Serilog;
using Serilog.Configuration;
using Serilog.Core;
using Serilog.Events;

var logSink = new InMemoryLogSink();
var logger = new LoggerConfiguration()
    .WriteTo.Sink(logSink)
    .CreateLogger();

logger.Information("This is an informational message");

IEnumerable<LogEvent> emits = logSink.CurrentLogEmits;
IEnumeratble<string> messages = logSink.CurrentLogMessages;

Serilog xUnit log sink

The Arcus.Testing.Logging library provides a XunitTestLogSink which is a Serilog log sink that delegates written log emits to the xUnit test output. This can help in testing logging infrastructure as the xUnit test output will contain the information that is being tested.

using Serilog;
using Serilog.Configuration;

// Injected in your test class.
ITestOutputHelper outputWriter = ...

var logger = new LoggerConfiguration()
    .WriteTo.XunitTestLogging(outputWriter)
    .CreateLogger();

logger.Information("This informational message will be delegated to the xUnit test output");