Addd new API TestContext.WriteLine(string message).

src/Adapter/MSTestAdapter.PlatformServices.Desktop/Services/DesktopTestContextImplementation.cs

@@ -19,7 +19,7 @@ namespace Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices
     using System.Linq;
 
     using Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices.Deployment;
-    
+
     /// <summary>
     /// Internal implementation of TestContext exposed to the user.
     /// The virtual string properties of the TestContext are retreived from the property dictionary
@@ -269,6 +269,32 @@ public override void EndTimer(string timerName)
             throw new NotSupportedException();
         }
 
+        //
+        // Summary:
+        //     When overridden in a derived class, used to write trace messages while the
+        //     test is running.
+        //
+        // Parameters:
+        //   message:
+        //     The formatted string that contains the trace message.
+        public override void WriteLine(string message)
+        {
+            if (this.stringWriterDisposed)
+            {
+                return;
+            }
+
+            try
+            {
+                var msg = message?.Replace("\0", "\\0");
+                stringWriter.WriteLine(msg);
+            }
+            catch (ObjectDisposedException)
+            {
+                this.stringWriterDisposed = true;
+            }
+        }
+
         //
         // Summary:
         //     When overridden in a derived class, used to write trace messages while the

src/TestFramework/UnitTestFramework.Extension.Desktop/TestContext.cs

@@ -15,6 +15,12 @@ namespace Microsoft.VisualStudio.TestTools.UnitTesting
     /// </summary>
     public abstract class TestContext
     {
+        /// <summary>
+        /// Used to write trace messages while the test is running
+        /// </summary>
+        /// <param name="message">formatted message string</param>
+        public abstract void WriteLine(string message);
+
         /// <summary>
         /// Used to write trace messages while the test is running
         /// </summary>

test/UnitTests/MSTestAdapter.PlatformServices.Desktop.Tests/Services/DesktopTestContextImplTests.cs

@@ -251,5 +251,40 @@ public void WriteLineShouldNotThrowIfStringWriterIsDisposed()
             // Calling it twice to cover the direct return when we know the object has been disposed.
             this.testContextImplementation.WriteLine("{0} Testing write", 1);
         }
+
+        [TestMethod]
+        public void WriteLineWithMessageShouldWriteToStringWriter()
+        {
+            var stringWriter = new StringWriter();
+            this.testContextImplementation = new TestContextImplementation(this.testMethod.Object, stringWriter, this.properties);
+
+            this.testContextImplementation.WriteLine("1 Testing write");
+
+            StringAssert.Contains(stringWriter.ToString(), "1 Testing write");
+        }
+
+        [TestMethod]
+        public void WriteLineWithMessageShouldWriteToStringWriterForNullCharacters()
+        {
+            var stringWriter = new StringWriter();
+            this.testContextImplementation = new TestContextImplementation(this.testMethod.Object, stringWriter, this.properties);
+
+            this.testContextImplementation.WriteLine("1 Testing \0 write \0");
+
+            StringAssert.Contains(stringWriter.ToString(), "1 Testing \\0 write \\0");
+        }
+
+        [TestMethod]
+        public void WriteLineWithMessageShouldNotThrowIfStringWriterIsDisposed()
+        {
+            var stringWriter = new StringWriter();
+            this.testContextImplementation = new TestContextImplementation(this.testMethod.Object, stringWriter, this.properties);
+
+            stringWriter.Dispose();
+
+            this.testContextImplementation.WriteLine("1 Testing write");
+            // Calling it twice to cover the direct return when we know the object has been disposed.
+            this.testContextImplementation.WriteLine("1 Testing write");
+        }
     }
 }