atwayne / test-logger

A utility class to assert `ILogger<T>` calls in unit tests

Dubstep.TestUtilities.TestLogger

Create a Microsoft.Extensions.Logging.ILogger<T> instance and assert log calls.

By default, LogXXX methods (e.g. LogDebug, LogException) are non-virtual members of a ILogger class, making it difficult to substituted. ^Link

This package is created to make it eaiser to verify your log calls in unit tests. It holds a list of all the log statements and expose the list so you can perform asserts on it.

LogStatements exposes the entire list while LastStatement expose the last call.

Usage

dotnet add package Dubstep.TestUtilities.TestLogger

[Test]
public void Should_Log_ExpectedMessage()
{
    // Arrange
    var loggerStub = new TestLogger<DubstepService>();
    var service = new DubstepService(loggerStub);
    var expectedMessage = "Task Completed."

    // Act
    service.DoSomethingAndLog();
    // loggerStub.LogDebug("Task Completed.");

    // Assert
    Assert.AreEqual(LogLevel.Debug, loggerStub.LastStatement.Level);
    Assert.AreEqual(expectedMessage, loggerStub.LastStatement.Message);
    // Or check `loggerStub.LogStatements` for complex asserts
}

[Test]
public void Should_Log_Exception()
{
    // Arrange
    var loggerStub = new TestLogger<DubstepService>();
    var service = new DubstepService(loggerStub);
    var expectedMessage = "Failed."

    // Act
    service.DoSomethingAndLogException();
    // loggerStub.LogError(exception, "Failed.");

    // Assert
    Assert.AreEqual(LogLevel.Error, loggerStub.LastStatement.Level);
    Assert.AreEqual(expectedMessage, loggerStub.LastStatement.Message);
    var exception = loggerStub.LastStatement.Exception;
    // add some asserts on the exception. `Type`, `Message`, `InnerException` etc.
}