Fix live output with HotReload

src/Platform/Microsoft.Testing.Platform/OutputDevice/IHotReloadPlatformOutputDevice.cs

@@ -0,0 +1,11 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.Testing.Platform.OutputDevice;
+
+internal interface IHotReloadPlatformOutputDevice : IPlatformOutputDevice
+{
+    Task DisplayBeforeHotReloadSessionStartAsync();
+
+    Task DisplayAfterHotReloadSessionEndAsync();
+}

src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/AnsiTerminalTestProgressFrame.cs

@@ -177,7 +177,12 @@ public void Render(AnsiTerminalTestProgressFrame previousFrame, AnsiTerminal ter
             terminal.MoveCursorUp(previousFrame.ProgressCount + 2);
         }
 
-        terminal.AppendLine();
+        // When there is nothing to render, don't write empty lines, e.g. when we start the test run, and then we kick off build
+        // in dotnet test, there is a long pause where we have no assemblies and no test results (yet).
+        if (ProgressCount > 0)
+        {
+            terminal.AppendLine();
+        }
 
         int i = 0;
         for (; i < ProgressCount; i++)

src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/TerminalTestReporter.cs

@@ -50,6 +50,8 @@ internal sealed partial class TerminalTestReporter : IDisposable
 
     private bool _wasCancelled;
 
+    private bool? _shouldShowPassedTests;
+
 #if NET7_0_OR_GREATER
     [GeneratedRegex(@$"^   at ((?<code>.+) in (?<file>.+):line (?<line>\d+)|(?<code1>.+))$", RegexOptions.ExplicitCapture, 1000)]
     private static partial Regex GetFrameRegex();
@@ -399,7 +401,7 @@ internal void TestCompleted(
         }
 
         _terminalWithProgress.UpdateWorker(asm.SlotIndex);
-        if (outcome != TestOutcome.Passed || _options.ShowPassedTests)
+        if (outcome != TestOutcome.Passed || GetShowPassedTests())
         {
             _terminalWithProgress.WriteToTerminal(terminal => RenderTestCompleted(
                 terminal,
@@ -416,6 +418,12 @@ internal void TestCompleted(
         }
     }
 
+    private bool GetShowPassedTests()
+    {
+        _shouldShowPassedTests ??= _options.ShowPassedTests();
+        return _shouldShowPassedTests.Value;
+    }
+
     internal /* for testing */ void RenderTestCompleted(
         ITerminal terminal,
         string assembly,
@@ -429,7 +437,7 @@ internal void TestCompleted(
         string? expected,
         string? actual)
     {
-        if (outcome == TestOutcome.Passed && !_options.ShowPassedTests)
+        if (outcome == TestOutcome.Passed && !GetShowPassedTests())
         {
             return;
         }

src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/TerminalTestReporterOptions.cs

@@ -13,7 +13,7 @@ internal sealed class TerminalTestReporterOptions
     /// <summary>
     /// Gets a value indicating whether we should show passed tests.
     /// </summary>
-    public bool ShowPassedTests { get; init; }
+    public Func<bool> ShowPassedTests { get; init; } = () => true;
 
     /// <summary>
     /// Gets a value indicating whether we should show information about which assembly is the source of the data on screen. Turn this off when running directly from an exe to reduce noise, because the path will always be the same.

src/Platform/Microsoft.Testing.Platform/OutputDevice/TerminalOutputDevice.cs

@@ -25,7 +25,7 @@ namespace Microsoft.Testing.Platform.OutputDevice;
 /// <summary>
 /// Implementation of output device that writes to terminal with progress and optionally with ANSI.
 /// </summary>
-internal partial class TerminalOutputDevice : IPlatformOutputDevice,
+internal partial class TerminalOutputDevice : IHotReloadPlatformOutputDevice,
     IDataConsumer,
     IOutputDeviceDataProducer,
     ITestSessionLifetimeHandler,
@@ -123,11 +123,16 @@ public Task InitializeAsync()
         bool noAnsi = _commandLineOptions.IsOptionSet(TerminalTestReporterCommandLineOptionsProvider.NoAnsiOption);
         bool noProgress = _commandLineOptions.IsOptionSet(TerminalTestReporterCommandLineOptionsProvider.NoProgressOption);
 
-        bool showPassed = false;
+        // _runtimeFeature.IsHotReloadEnabled is not set to true here, even if the session will be HotReload,
+        // we need to postpone that decision until the first test result.
+        //
+        // This works but is NOT USED, we prefer to have the same experience of not showing passed tests in hotReload mode as in normal mode.
+        // Func<bool> showPassed = () => _runtimeFeature.IsHotReloadEnabled;
+        Func<bool> showPassed = () => false;
         bool outputOption = _commandLineOptions.TryGetOptionArgumentList(TerminalTestReporterCommandLineOptionsProvider.OutputOption, out string[]? arguments);
         if (outputOption && arguments?.Length > 0 && TerminalTestReporterCommandLineOptionsProvider.OutputOptionDetailedArgument.Equals(arguments[0], StringComparison.OrdinalIgnoreCase))
         {
-            showPassed = true;
+            showPassed = () => true;
         }
 
         Func<bool?> shouldShowProgress = noProgress
@@ -270,6 +275,9 @@ public virtual async Task DisplayBannerAsync(string? bannerMessage)
         }
     }
 
+    public async Task DisplayBeforeHotReloadSessionStartAsync()
+        => await DisplayBeforeSessionStartAsync();
+
     public async Task DisplayBeforeSessionStartAsync()
     {
         RoslynDebug.Assert(_terminalTestReporter is not null);
@@ -284,15 +292,30 @@ public async Task DisplayBeforeSessionStartAsync()
         }
     }
 
+    public async Task DisplayAfterHotReloadSessionEndAsync()
+        => await DisplayAfterSessionEndRunInternalAsync();
+
     public async Task DisplayAfterSessionEndRunAsync()
     {
-        RoslynDebug.Assert(_terminalTestReporter is not null);
-
         if (_isVSTestMode || _isListTests || _isServerMode)
         {
             return;
         }
 
+        // Do NOT check and store the value in the constructor
+        // it won't be populated yet, so you will always see false.
+        if (_runtimeFeature.IsHotReloadEnabled)
+        {
+            return;
+        }
+
+        await DisplayAfterSessionEndRunInternalAsync();
+    }
+
+    private async Task DisplayAfterSessionEndRunInternalAsync()
+    {
+        RoslynDebug.Assert(_terminalTestReporter is not null);
+
         using (await _asyncMonitor.LockAsync(TimeoutHelper.DefaultHangTimeSpanTimeout))
         {
             if (!_firstCallTo_OnSessionStartingAsync)

test/UnitTests/Microsoft.Testing.Platform.UnitTests/OutputDevice/Terminal/TerminalTestReporterTests.cs

@@ -47,7 +47,7 @@ public void OutputFormattingIsCorrect()
         var stringBuilderConsole = new StringBuilderConsole();
         var terminalReporter = new TerminalTestReporter(stringBuilderConsole, new TerminalTestReporterOptions
         {
-            ShowPassedTests = true,
+            ShowPassedTests = () => true,
             UseAnsi = true,
             ForceAnsi = true,