Issue #4686: Add ProgressTraceListener

src/NUnitFramework/framework/Diagnostics/ProgressTraceListener.cs

@@ -0,0 +1,60 @@
+// Copyright (c) Charlie Poole, Rob Prouse and Contributors. MIT License - see LICENSE.txt
+
+using System;
+using System.Diagnostics;
+#if !NET6_0_OR_GREATER
+using System.Security.Permissions;
+#endif
+
+namespace NUnit.Framework.Diagnostics
+{
+    /// <summary><para>
+    /// The ProgressTraceListener class allows directing tracing or
+    /// debugging output to <see cref="TestContext.Progress"/>.
+    /// </para><para>
+    /// To activate, place the following snippet into the one-time
+    /// set-up method of either a test's fixture or the set-up
+    /// fixture of a project:
+    /// <c>
+    /// System.Trace.Listeners.Add(new ProgressTraceListener());
+    /// </c>
+    /// </para><para>
+    /// Make sure to only add a listener once, e.g.:
+    /// <c>
+    /// if (!System.Trace.Listeners.OfType&lt;ProgressTraceListener&gt;().Any())
+    ///     System.Trace.Listeners.Add(new ProgressTraceListener());
+    /// </c>
+    /// </para><para>
+    /// Or again remove in the one-time tear-down, e.g.:
+    /// <c>
+    /// System.Trace.Listeners.Remove(_progressTraceListener);
+    /// </c>
+    /// </para></summary>
+    /// <remarks><para>
+    /// Although named "Trace", <see cref="TextWriterTraceListener"/>
+    /// "directs tracing or debugging output".
+    /// </para><para>
+    /// This listener is provided by NUnit (i.e. the origin of
+    /// <see cref="TestContext.Progress"/>) same as the
+    /// <see cref="ConsoleTraceListener"/> is provided by .NET
+    /// (the origin of <see cref="Console"/>).
+    /// </para></remarks>
+    // Implemented following the ConsoleTraceListener implementation.
+#if !NET6_0_OR_GREATER
+    [HostProtection(Synchronization = true)]
+#endif
+    public class ProgressTraceListener : TextWriterTraceListener
+    {
+        #region Constructors
+
+        /// <summary>
+        /// Construct a ProgressTraceListener with trace
+        /// output written to <see cref="TestContext.Progress"/>
+        /// </summary>
+        public ProgressTraceListener() : base(TestContext.Progress)
+        {
+        }
+
+        #endregion
+    }
+}

src/NUnitFramework/tests/Diagnostics/ProgressTraceListenerTests.cs

@@ -0,0 +1,144 @@
+// Copyright (c) Charlie Poole, Rob Prouse and Contributors. MIT License - see LICENSE.txt
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using NUnit.Framework.Diagnostics;
+using NUnit.Framework.Interfaces;
+using NUnit.Framework.Internal;
+
+namespace NUnit.Framework.Tests.Diagnostics
+{
+    public abstract class ProgressTraceListenerTestsBase
+    {
+        protected const string SOME_TEXT = "Should go to the output";
+        protected static readonly string NL = Environment.NewLine;
+
+        protected TestListenerInterceptor TestResultListener { get; private set; }
+
+        [SetUp]
+        public void AddTestResultListener()
+        {
+            // Wrap the current listener, listening to events, and forwarding the original event
+            TestResultListener = new TestListenerInterceptor(TestExecutionContext.CurrentContext.Listener);
+            TestExecutionContext.CurrentContext.Listener = TestResultListener;
+        }
+
+        [TearDown]
+        public void RemoveTestResultListener()
+        {
+            // Restore the original listener
+            TestExecutionContext.CurrentContext.Listener = TestResultListener.DefaultListener;
+        }
+
+        [Test]
+        public void TestProgressIsOutput()
+        {
+            Assert.That(TestResultListener.Outputs, Has.Count.EqualTo(0));
+
+            TestContext.Progress.WriteLine(SOME_TEXT);
+            Assert.That(TestResultListener.Outputs, Has.Count.EqualTo(1));
+            Assert.That(TestResultListener.Outputs[0], Is.EqualTo(SOME_TEXT + NL));
+        }
+
+        #region ITestListener implementation
+
+        protected class TestListenerInterceptor : ITestListener
+        {
+            public IList<string> Outputs { get; }
+            public ITestListener DefaultListener { get; }
+
+            public TestListenerInterceptor(ITestListener defaultListener)
+            {
+                DefaultListener = defaultListener;
+                Outputs = new List<string>();
+            }
+
+            void ITestListener.TestStarted(ITest test)
+            {
+                DefaultListener?.TestStarted(test);
+            }
+
+            void ITestListener.TestFinished(ITestResult result)
+            {
+                DefaultListener?.TestFinished(result);
+            }
+
+            void ITestListener.TestOutput(TestOutput output)
+            {
+                Assert.That(output, Is.Not.Null);
+                Outputs.Add(output.Text);
+
+                DefaultListener?.TestOutput(output);
+            }
+
+            void ITestListener.SendMessage(TestMessage message)
+            {
+            }
+        }
+
+        #endregion
+    }
+
+    [TestFixture, NonParallelizable] // Adding the "ProgressTraceListener" may lead to side-effects in other tests.
+    public class ProgressTraceListenerTests : ProgressTraceListenerTestsBase
+    {
+        private ProgressTraceListener _progressTraceListener;
+
+        [OneTimeSetUp]
+        public void AddProgressTraceListener()
+        {
+            _progressTraceListener = new ProgressTraceListener();
+            Trace.Listeners.Add(_progressTraceListener);
+        }
+
+        [OneTimeTearDown]
+        public void RemoveProgressTraceListener()
+        {
+            Trace.Listeners.Remove(_progressTraceListener);
+            _progressTraceListener.Dispose();
+        }
+
+        [Test]
+        public void TestDebugIsDirectedToOutput()
+        {
+            Assert.That(TestResultListener.Outputs, Has.Count.EqualTo(0));
+
+            Debug.WriteLine(SOME_TEXT);
+            Assert.That(TestResultListener.Outputs, Has.Count.EqualTo(1));
+            Assert.That(TestResultListener.Outputs[0], Is.EqualTo(SOME_TEXT + NL));
+        }
+
+        [Test]
+        public void TestTraceIsDirectedToOutput()
+        {
+            Assert.That(TestResultListener.Outputs, Has.Count.EqualTo(0));
+
+            Trace.WriteLine(SOME_TEXT);
+            Assert.That(TestResultListener.Outputs, Has.Count.EqualTo(1));
+            Assert.That(TestResultListener.Outputs[0], Is.EqualTo(SOME_TEXT + NL));
+        }
+    }
+
+    [TestFixture, NonParallelizable] // Tests may be affected by adding the "ProgressTraceListener" in "ProgressTraceListenerTests".
+    public class NoProgressTraceListenerTests : ProgressTraceListenerTestsBase
+    {
+        [Test]
+        public void TestDebugIsNotDirectedToOutput()
+        {
+            Assert.That(TestResultListener.Outputs, Has.Count.EqualTo(0));
+
+            Debug.WriteLine(SOME_TEXT);
+            Assert.That(TestResultListener.Outputs, Has.Count.EqualTo(0));
+        }
+
+        [Test]
+        public void TestTraceIsNotDirectedToOutput()
+        {
+            Assert.That(TestResultListener.Outputs, Has.Count.EqualTo(0));
+
+            Trace.WriteLine(SOME_TEXT);
+            Assert.That(TestResultListener.Outputs, Has.Count.EqualTo(0));
+        }
+    }
+}