log4net TestContextAppender

TestContextAppender.cs

using log4net.Appender;
using log4net.Core;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;

namespace XXX.Framework.Logging
{
    /// <summary>
    /// Simple appender, writing all logging events to the given <c>TestContext</c>.
    /// </summary>
    public sealed class TestContextAppender : AppenderSkeleton
    {
        #region Fields
        // ----------------------------------------------------------------------------------------
        // Fields
        // ----------------------------------------------------------------------------------------

        public const string DefaultAppenderName = "TestContextAppender";

        // ----------------------------------------------------------------------------------------
        #endregion // Fields

        #region constructor

        /// <summary>
        /// Creates an instance of the class <c>TestContextAppender</c>.
        /// </summary>
        /// <param name="testContext">The current <c>TestContext</c> as target for logging events.</param>
        /// <param name="appenderName">Name of the appender.</param>
        public TestContextAppender(TestContext testContext, string appenderName = DefaultAppenderName)
            : base()
        {
            this.TestContext = testContext;
            this.TestContext.Properties[appenderName] = this;
        }

        #endregion

        #region IAppender members

        /// <summary>
        /// Write a logging event to the <c>TestContext</c>.
        /// </summary>
        /// <param name="loggingEvent">The logging event to write to the <c>TestContext</c>.</param>
        protected override void Append(LoggingEvent loggingEvent)
        {
            var message = String.Format(
                "Log [{0}]: {1}, Exception: {2}",
                loggingEvent.Level,
                loggingEvent.RenderedMessage,
                loggingEvent.ExceptionObject
            );

            this.TestContext.WriteLine(message);
            this.LoggingOutput += message;

            if (loggingEvent.Level >= Level.Warn)
            {
                this.IsWarningOrErrorLogged = true;
            }
        }

        #endregion

        #region TestContextAppender members
        // ----------------------------------------------------------------------------------------
        // TestContextAppender members
        // ----------------------------------------------------------------------------------------

        /// <summary>
        /// Gets the instance of the appender from the test context.
        /// </summary>
        /// <param name="testContext">The test context.</param>
        /// <param name="appenderName">Name of the appender.</param>
        /// <returns></returns>
        public static TestContextAppender GetFromTestContext(TestContext testContext, string appenderName = DefaultAppenderName)
        {
            return testContext.Properties[appenderName] as TestContextAppender;
        }

        /// <summary>
        /// Asserts the default checks:
        /// * The logger has been initialized.
        /// * No warning or error has been logged.
        /// For further tests get an instance with GetFromTestContext().
        /// </summary>
        /// <param name="testContext">The test context.</param>
        /// <param name="appenderName">Name of the appender.</param>
        public static void AssertDefaults(TestContext testContext, string appenderName = DefaultAppenderName)
        {
            var self = GetFromTestContext(testContext, appenderName);

            Assert.IsNotNull(self);

            self.AssertNoWarningOrErrorLogged();
        }

        /// <summary>
        /// Gets or sets the test context.
        /// </summary>
        /// <value>
        /// The test context.
        /// </value>
        public TestContext TestContext { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether this instance is warning or error logged.
        /// </summary>
        /// <value>
        /// 	<c>true</c> if this instance is warning or error logged; otherwise, <c>false</c>.
        /// </value>
        public bool IsWarningOrErrorLogged { get; set; }

        /// <summary>
        /// Gets or sets the logging output.
        /// </summary>
        /// <value>
        /// The logging output.
        /// </value>
        public string LoggingOutput { get; set; }

        /// <summary>
        /// Asserts that no warning or error has been logged.
        /// </summary>
        public void AssertNoWarningOrErrorLogged()
        {
            Assert.IsFalse(this.IsWarningOrErrorLogged, String.Format("Error or warnings have been logged: {0}", this.LoggingOutput));
        }

        /// <summary>
        /// Asserts the logging output not empty.
        /// </summary>
        public void AssertLoggingOutputNotEmpty()
        {
            Assert.IsFalse(String.IsNullOrEmpty(this.LoggingOutput), String.Format("The logging output is not empty: {0}", this.LoggingOutput));
        }

        // ----------------------------------------------------------------------------------------
        #endregion // TestContextAppender members
    }
}