RandomSkunk.EasyLogger 1.0.0-rc1

RandomSkunk.EasyLogging

This library provides two simple logger base classes, EasyLogger and EasyLogger<TCategoryName>, which implement ILogger and ILogger<TCategoryName> respectively.

What makes it an "easy" logger?

• Correctly implementing the ILogger.BeginScope method is difficult.
  • EasyLogger takes care of it for you.
• Implementing ILogger.IsEnabled isn't terribly difficult, but if you're not careful, you could end up writing logs at the None log level.
  • EasyLogger implements this method and doesn't accidentally write None logs.
• Mocking the ILogger.Log in order to verify that a logging operation took place is difficult.
  • First, you need to deal with the generic type argument and the state parameter. It could be literally any type and any value. Where do you even begin?
  • What is the formatter parameter all about?
  • What about the logger's scope? What if you wanted to verify that the logger had a certain scope at the time of the log event? How would you mock that?
  • Mocking the EasyLogger.Write method to verify that a logging operation took place is easy.
• The ease of mocking is tested and verified with Moq, FakeItEasy, and NSubstitute.

Mock Logger Setup and Verification

EasyLogger is easy to mock regardless of the mocking library - just specify that its abstract Write method should be the target for setup or verification.

Note that the LogEntry struct contains numerous methods for querying whether it is a match for a setup or verification. Methods used below in the examples are IsInformation, HasMessage, and HasAttribute.

Moq

Mock<EasyLogger> mockLogger = new Mock<EasyLogger>();
EasyLogger logger = mockLogger.Object;

LogEntry? capturedLogEntry = null;

// Setup
mockLogger.Setup(m => m.Write(It.IsAny<LogEntry>()))
    .Callback<LogEntry>(logEntry => capturedLogEntry = logEntry);

logger.LogInformation("Hello, {Who}!", "world");

// Verification
mockLogger.Verify(m => m.Write(It.Is<LogEntry>(log =>
    log.IsInformation() && log.HasMessage("Hello, world!") && log.HasAttribute("Who", "world"))));

FakeItEasy

EasyLogger logger = A.Fake<EasyLogger>();

LogEntry? capturedLogEntry = null;

// Setup
A.CallTo(() => logger.Write(A<LogEntry>.Ignored))
    .Invokes((LogEntry logEntry) => capturedLogEntry = logEntry);

logger.LogInformation("Hello, {Who}!", "world");

// Verification
A.CallTo(() => logger.Write(A<LogEntry>.That.Matches(log =>
    log.IsInformation() && log.HasMessage("Hello, world!") && log.HasAttribute("Who", "world"))))
    .MustHaveHappened();

NSubstitute

EasyLogger logger = Substitute.For<EasyLogger>();

LogEntry? capturedLogEntry = null;

// Setup
logger.When(m => m.Write(Arg.Any<LogEntry>()))
    .Do(x => capturedLogEntry = x.Arg<LogEntry>());

logger.LogInformation("Hello, {Who}!", "world");

// Verification
logger.Received().Write(Arg.Is<LogEntry>(log =>
    log.IsInformation() && log.HasMessage("Hello, world!") && log.HasAttribute("Who", "world")));