Fixes #3956. Refactor unit test projects: rename UnitTests→Legacy, add NonParallelizable, eliminate Legacy tests

.github/workflows/README.md

@@ -29,8 +29,9 @@ The repository uses multiple GitHub Actions workflows. What runs and when:
 1. Each OS checks out code, restores, and builds locally
 2. **Performance optimizations**:
    - Disables Windows Defender on Windows runners (significant speedup)
-3. Runs two test jobs:
-   - **Non-parallel UnitTests**: `Tests/UnitTests` with diagnostic output
+3. Runs three test jobs:
+   - **Non-parallel UnitTests.Legacy**: `Tests/UnitTests.Legacy` with diagnostic output
+   - **Non-parallel UnitTests.NonParallelizable**: `Tests/UnitTests.NonParallelizable` with diagnostic output
    - **Parallel UnitTestsParallelizable**: `Tests/UnitTestsParallelizable` with diagnostic output
 4. Uploads test logs and diagnostic data from all runners
 
@@ -87,7 +88,8 @@ The repository uses multiple GitHub Actions workflows. What runs and when:
 # Full CI sequence:
 dotnet restore
 dotnet build --configuration Debug --no-restore
-dotnet test --project Tests/UnitTests --no-build --verbosity normal
+dotnet test --project Tests/UnitTests.Legacy --no-build --verbosity normal
+dotnet test --project Tests/UnitTests.NonParallelizable --no-build --verbosity normal
 dotnet test --project Tests/UnitTestsParallelizable --no-build --verbosity normal
 dotnet build --configuration Release --no-restore
 ```

.github/workflows/unit-tests.yml

@@ -47,23 +47,23 @@ jobs:
         Add-MpPreference -ExclusionPath "${{ github.workspace }}"
         Add-MpPreference -ExclusionProcess "dotnet.exe"
 
-    - name: Run UnitTests
+    - name: Run UnitTests.NonParallelizable
       shell: bash
       run: |
         dotnet test \
-          --project Tests/UnitTests \
+          --project Tests/UnitTests.NonParallelizable \
           --no-build \
           --verbosity normal \
-          --diagnostic --diagnostic-output-directory logs/UnitTests/${{ runner.os }}
+          --diagnostic --diagnostic-output-directory logs/UnitTests.NonParallelizable/${{ runner.os }}
 
     - name: Upload Test Logs
       if: always()
       uses: actions/upload-artifact@v4
       with:
         name: non_parallel_unittests-logs-${{ runner.os }}
         path: |
-          logs/UnitTests/
-          Tests/UnitTests/logs/
+          logs/UnitTests.NonParallelizable/
+          Tests/UnitTests.NonParallelizable/logs/
           TestResults/
           **/*.dmp
         if-no-files-found: ignore

Terminal.Gui/Terminal.Gui.csproj

@@ -83,6 +83,8 @@
     <ItemGroup>
         <InternalsVisibleTo Include="Benchmarks" />
         <InternalsVisibleTo Include="UnitTests" />
+        <InternalsVisibleTo Include="UnitTests.Legacy" />
+        <InternalsVisibleTo Include="UnitTests.NonParallelizable" />
         <InternalsVisibleTo Include="UnitTests.Parallelizable" />
         <InternalsVisibleTo Include="StressTests" />
         <InternalsVisibleTo Include="IntegrationTests" />

Terminal.sln

@@ -105,7 +105,9 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NativeAot", "Examples\Nativ
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Benchmarks", "Tests\Benchmarks\Benchmarks.csproj", "{242FBD3E-2EC6-4274-BD40-8E62AF9327B2}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "UnitTests", "Tests\UnitTests\UnitTests.csproj", "{038B09F5-EF3A-F21E-7C10-A6551866ECE2}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "UnitTests.Legacy", "Tests\UnitTests.Legacy\UnitTests.Legacy.csproj", "{038B09F5-EF3A-F21E-7C10-A6551866ECE2}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "UnitTests.NonParallelizable", "Tests\UnitTests.NonParallelizable\UnitTests.NonParallelizable.csproj", "{B7C94F2A-3E8D-4A1B-9F5C-2D1E6A3B7C90}"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "IntegrationTests", "Tests\IntegrationTests\IntegrationTests.csproj", "{F74EC349-B988-FCFA-A1E5-967F70FB75B5}"
 EndProject
@@ -123,7 +125,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Testing", "Testing", "{1A3C
 	ProjectSection(SolutionItems) = preProject
 		codecov.yml = codecov.yml
 		Scripts\Run-LocalCoverage.ps1 = Scripts\Run-LocalCoverage.ps1
-		Tests\UnitTests\runsettings.xml = Tests\UnitTests\runsettings.xml
+		Tests\UnitTests.Legacy\runsettings.xml = Tests\UnitTests.Legacy\runsettings.xml
 	EndProjectSection
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "FluentExample", "Examples\FluentExample\FluentExample.csproj", "{8C05292F-86C9-C29A-635B-A4DFC5955D1C}"
@@ -189,6 +191,10 @@ Global
 		{038B09F5-EF3A-F21E-7C10-A6551866ECE2}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{038B09F5-EF3A-F21E-7C10-A6551866ECE2}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{038B09F5-EF3A-F21E-7C10-A6551866ECE2}.Release|Any CPU.Build.0 = Release|Any CPU
+		{B7C94F2A-3E8D-4A1B-9F5C-2D1E6A3B7C90}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B7C94F2A-3E8D-4A1B-9F5C-2D1E6A3B7C90}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B7C94F2A-3E8D-4A1B-9F5C-2D1E6A3B7C90}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B7C94F2A-3E8D-4A1B-9F5C-2D1E6A3B7C90}.Release|Any CPU.Build.0 = Release|Any CPU
 		{F74EC349-B988-FCFA-A1E5-967F70FB75B5}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{F74EC349-B988-FCFA-A1E5-967F70FB75B5}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{F74EC349-B988-FCFA-A1E5-967F70FB75B5}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -248,6 +254,7 @@ Global
 		{E6D716C6-AC94-4150-B10A-44AE13F79344} = {3DD033C0-E023-47BF-A808-9CCE30873C3E}
 		{242FBD3E-2EC6-4274-BD40-8E62AF9327B2} = {A589126F-C71A-4FEE-B7EA-2DCA1ADF6A46}
 		{038B09F5-EF3A-F21E-7C10-A6551866ECE2} = {A589126F-C71A-4FEE-B7EA-2DCA1ADF6A46}
+		{B7C94F2A-3E8D-4A1B-9F5C-2D1E6A3B7C90} = {A589126F-C71A-4FEE-B7EA-2DCA1ADF6A46}
 		{F74EC349-B988-FCFA-A1E5-967F70FB75B5} = {A589126F-C71A-4FEE-B7EA-2DCA1ADF6A46}
 		{96ACE8BA-2E07-7537-FBF2-E8176CCB8080} = {A589126F-C71A-4FEE-B7EA-2DCA1ADF6A46}
 		{DE780834-190A-8277-51FD-750CC666E82D} = {A589126F-C71A-4FEE-B7EA-2DCA1ADF6A46}

Tests/IntegrationTests/IntegrationTests.csproj

@@ -34,7 +34,7 @@
         <ProjectReference Include="..\..\Tests\AppTestHelpers.XunitHelpers\AppTestHelpers.XunitHelpers.csproj" />
         <ProjectReference Include="..\..\Tests\AppTestHelpers\AppTestHelpers.csproj" />
         <ProjectReference Include="..\..\Examples\UICatalog\UICatalog.csproj" />
-        <ProjectReference Include="..\UnitTests\UnitTests.csproj" />
+        <ProjectReference Include="..\UnitTests.Legacy\UnitTests.Legacy.csproj" />
     </ItemGroup>
     <ItemGroup>
         <Using Include="Xunit" />

Tests/README.md

@@ -2,28 +2,90 @@
 
 This folder contains the tests for Terminal.Gui.
 
-## ./UnitTests
+## Test Projects
 
-This folder contains the unit tests for Terminal.Gui that can not be run in parallel. This is because they
-depend on `Application` or other class that use static state or `ConfigurationManager`.
+### ./UnitTestsParallelizable
 
-We should be striving to move as many tests as possible to the `./UnitTestsParallelizable` folder.
+The primary home for new tests. Tests here run in parallel (`parallelizeAssembly: true`, `maxParallelThreads: 12`)
+and **must not** touch any process-wide static state.
 
-## ./UnitTestsParallelizable
+### ./UnitTests.NonParallelizable
 
-This folder contains the unit tests for Terminal.Gui that can be run in parallel.
+Tests that either explicitly test process-wide static state, or must set process-wide statics, or otherwise
+cannot be run concurrently with other tests. These tests run with `parallelizeAssembly: false`.
 
-## ./IntegrationTests
+### ./UnitTests.Legacy
 
-This folder contains the integration tests for Terminal.Gui.
+Tests that have not yet been ported to `UnitTestsParallelizable` or `UnitTests.NonParallelizable`.
+These tests are candidates for rewrite (if the case is not covered elsewhere) or deletion (if already covered).
+Do not add new tests here.
 
-## ./StressTests
+### ./IntegrationTests
 
-This folder contains the stress tests for Terminal.Gui.
+Integration tests for Terminal.Gui.
 
-## ./PerformanceTests
+### ./StressTests
 
-This folder WILL contain the performance tests for Terminal.Gui.
+Stress tests for Terminal.Gui.
 
+---
+
+## Static State in Terminal.Gui
+
+The following classes and properties use process-wide static state. Tests that read or write these **must not**
+go in `UnitTestsParallelizable` — they belong in `UnitTests.NonParallelizable`.
+
+### `Application` (legacy static façade — `Terminal.Gui.App/Legacy/`)
+
+| Member | Notes |
+|--------|-------|
+| `Application.Instance` | Returns `ApplicationImpl.Instance` (singleton) |
+| `Application.Init(driverName)` | Initializes the singleton; sets `Initialized`, `Driver`, `MainThreadId`, `SynchronizationContext` |
+| `Application.Shutdown()` | Disposes the singleton; resets all static fields |
+| `Application.Initialized` | Global bool; true between `Init` and `Shutdown` |
+| `Application.MainThreadId` | Process-wide main thread ID set by `Init` |
+| `Application.Driver` | The active `IDriver` singleton |
+| `Application.DefaultKeyBindings` | Process-wide default key-binding dictionary (mutable `IDictionary`) |
+| `Application.ForceDriver` | Persists across tests unless reset |
+| `Application.Keyboard` | Delegates to `ApplicationImpl.Instance.Keyboard` |
+| `Application.Navigation` | Delegates to `ApplicationImpl.Instance.Navigation` |
+| `Application.Popovers` | Delegates to `ApplicationImpl.Instance.Popovers` |
+| `Application.Screen` | Delegates to `ApplicationImpl.Instance.Screen` |
+| `Application.ResetState()` | Resets all static backing fields to defaults |
+| `SynchronizationContext.Current` | Set by `Application.Init`; process-wide |
+
+### `ApplicationImpl` (singleton — `Terminal.Gui.App/ApplicationImpl.cs`)
+
+| Member | Notes |
+|--------|-------|
+| `ApplicationImpl.Instance` | Process-wide singleton; set by `SetInstance()` |
+| `ApplicationImpl.SetInstance(impl)` | Replaces the singleton (used in tests) |
+| `ApplicationImpl.ResetModelUsageTracking()` | Resets the static "which model was used" flag |
+
+### `ConfigurationManager` (singleton — `Terminal.Gui.Configuration/`)
+
+| Member | Notes |
+|--------|-------|
+| `CM.IsEnabled` | Global flag; affects all code reading configuration |
+| `CM.Disable(reset)` | Disables and optionally resets to hard-coded defaults |
+
+### `View.Diagnostics` (static field — `Terminal.Gui.ViewBase/View.cs`)
+
+| Member | Notes |
+|--------|-------|
+| `View.Diagnostics` | `ViewDiagnosticFlags`; process-wide debug flags |
+
+---
+
+## Which Project Does My Test Belong In?
+
+| Test characteristic | Project |
+|---------------------|---------|
+| No static state; no `Application.Init`/`Shutdown`; no `ConfigurationManager` mutations | `UnitTestsParallelizable` |
+| Calls `Application.Init`/`Shutdown` directly, or mutates `Application.DefaultKeyBindings`, `Application.ForceDriver`, or `ApplicationImpl.ResetModelUsageTracking()` | `UnitTests.NonParallelizable` |
+| Uses `[AutoInitShutdown]` or `[SetupFakeApplication]` (fake driver, does not call real `Application.Init`) | Currently in `UnitTests.Legacy`; migrate to `UnitTestsParallelizable` or `UnitTests.NonParallelizable` after review |
+| Not yet reviewed / ported | `UnitTests.Legacy` |
+
+---
 
 See the [Testing wiki](https://github.com/gui-cs/Terminal.Gui/wiki/Testing) for details on how to add more tests.

Tests/UnitTests.Legacy/README.md

@@ -0,0 +1,13 @@
+# UnitTests.Legacy
+
+This project contains tests that have not yet been ported to `UnitTestsParallelizable` or `UnitTests.NonParallelizable`.
+
+**Do not add new tests here.** New tests should go in:
+- [`../UnitTestsParallelizable`](../UnitTestsParallelizable/README.md) for tests with no static state dependency.
+- [`../UnitTests.NonParallelizable`](../UnitTests.NonParallelizable/README.md) for tests that explicitly depend on process-wide static state.
+
+Each test class in this project is a candidate for one of:
+1. **Rewrite** in the appropriate project if the case is not already covered.
+2. **Deletion** if the case is already covered in `UnitTestsParallelizable`.
+
+See the [Testing wiki](https://github.com/gui-cs/Terminal.Gui/wiki/Testing) for details.

Tests/UnitTests/UnitTests.csproj → Tests/UnitTests.Legacy/UnitTests.Legacy.csproj

@@ -9,6 +9,7 @@
 		<InformationalVersion>2.0</InformationalVersion>
 	</PropertyGroup>
 	<PropertyGroup>
+		<AssemblyName>UnitTests.Legacy</AssemblyName>
 		<OutputType>Exe</OutputType>
 		<UseAppHost>true</UseAppHost>
 		<IsTestProject>true</IsTestProject>

Tests/UnitTests/UnitTests.sln → Tests/UnitTests.Legacy/UnitTests.Legacy.sln

@@ -3,7 +3,7 @@ Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
 VisualStudioVersion = 17.5.002.0
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "UnitTests", "UnitTests.csproj", "{A29633F2-B26E-48B2-997A-1733286E3C13}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "UnitTests.Legacy", "UnitTests.Legacy.csproj", "{A29633F2-B26E-48B2-997A-1733286E3C13}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution

Tests/UnitTests/Application/ApplicationModelFencingTests.cs → Tests/UnitTests.NonParallelizable/Application/ApplicationModelFencingTests.cs

@@ -1,4 +1,4 @@
-namespace UnitTests.ApplicationTests;
+namespace UnitTests.NonParallelizable.ApplicationTests;
 
 /// <summary>
 ///     Tests to ensure that mixing legacy static Application and modern instance-based models

Tests/UnitTests/Application/Keyboard/ApplicationKeyboardThreadSafetyTests.cs → Tests/UnitTests.NonParallelizable/Application/Keyboard/ApplicationKeyboardThreadSafetyTests.cs

@@ -1,7 +1,7 @@
 #nullable enable
 // ReSharper disable AccessToDisposedClosure
 
-namespace UnitTests.ApplicationTests.Keyboard;
+namespace UnitTests.NonParallelizable.ApplicationTests.Keyboard;
 
 /// <summary>
 ///     Tests to verify that ApplicationKeyboard is thread-safe for concurrent access scenarios.

Tests/UnitTests/Application/Keyboard/KeyboardSetterTests.cs → Tests/UnitTests.NonParallelizable/Application/Keyboard/KeyboardSetterTests.cs

@@ -1,7 +1,7 @@
 // Tests that mutate Application.DefaultKeyBindings (static state).
 // These MUST NOT be in UnitTestsParallelizable.
 
-namespace UnitTests.ApplicationTests.Keyboard;
+namespace UnitTests.NonParallelizable.ApplicationTests.Keyboard;
 
 public class KeyboardSetterTests
 {

Tests/UnitTests.NonParallelizable/Application/SynchronizationContextTests.cs

@@ -0,0 +1,52 @@
+// Copilot
+#nullable enable
+
+namespace UnitTests.NonParallelizable.ApplicationTests;
+
+/// <summary>
+///     Tests for the <see cref="SynchronizationContext"/> that is set during the Terminal.Gui application lifecycle.
+///     Must run non-concurrently because <see cref="IApplication.Init"/> and <see cref="IDisposable.Dispose"/> mutate
+///     the process-wide <see cref="SynchronizationContext.Current"/>.
+/// </summary>
+public class SynchronizationContextTests
+{
+    [Fact]
+    public void Init_SetsSynchronizationContext_Dispose_ClearsIt ()
+    {
+        IApplication app = Application.Create ();
+
+        try
+        {
+            app.Init (DriverRegistry.Names.ANSI);
+
+            Assert.NotNull (SynchronizationContext.Current);
+        }
+        finally
+        {
+            app.Dispose ();
+        }
+
+        Assert.Null (SynchronizationContext.Current);
+    }
+
+    [Fact]
+    public void Init_SynchronizationContext_CreateCopy_ReturnsDifferentInstance ()
+    {
+        IApplication app = Application.Create ();
+
+        try
+        {
+            app.Init (DriverRegistry.Names.ANSI);
+
+            SynchronizationContext context = SynchronizationContext.Current!;
+            SynchronizationContext copy = context.CreateCopy ();
+
+            Assert.NotNull (copy);
+            Assert.NotSame (context, copy);
+        }
+        finally
+        {
+            app.Dispose ();
+        }
+    }
+}

Tests/UnitTests.NonParallelizable/AssemblyInfo.cs

@@ -0,0 +1,15 @@
+global using Attribute = Terminal.Gui.Drawing.Attribute;
+global using Color = Terminal.Gui.Drawing.Color;
+global using CM = Terminal.Gui.Configuration.ConfigurationManager;
+global using Terminal.Gui.App;
+global using Terminal.Gui.Time;
+global using Terminal.Gui.Testing;
+global using Terminal.Gui.Drivers;
+global using Terminal.Gui.Input;
+global using Terminal.Gui.Configuration;
+global using Terminal.Gui.ViewBase;
+global using Terminal.Gui.Views;
+global using Terminal.Gui.Drawing;
+global using Terminal.Gui.Text;
+global using Terminal.Gui.Resources;
+global using Terminal.Gui.FileServices;