Running Tests in the WinForms Repository

The repository uses xUnit v3 with Microsoft.Testing.Platform as its test framework. Tests are organized into unit tests and integration / functional tests.

Important: The test projects build as self-contained executables using Microsoft.Testing.Platform (not the legacy VSTest adapter). The dotnet test --filter flag and vstest.console.exe do not work with these projects. See sections 4 and 4b for the correct filtering syntax.

1 Running All Unit Tests

.\build.cmd -test

This builds the solution and executes every unit test project. Results appear in artifacts\TestResults\.

Release configuration

.\build.cmd -test -configuration Release

2 Running All Integration / Functional Tests

.\build.cmd -integrationTest

Functional tests open and close windows automatically — do not interact with the desktop while they run.

3 Running Tests for a Single Project

After a full build (.\build.cmd), navigate to the test project directory and use dotnet test:

# Unit tests for System.Windows.Forms
pushd src\test\unit\System.Windows.Forms
dotnet test

# Unit tests for System.Drawing.Common
pushd src\System.Drawing.Common\tests
dotnet test

# Unit tests for System.Windows.Forms.Primitives
pushd src\System.Windows.Forms.Primitives\tests\UnitTests
dotnet test

Tip: The repo-local SDK must be on your PATH. Run .\Restore.cmd or launch via .\start-code.cmd / .\start-vs.cmd.

Key test project paths

4 Running a Single Test or Filtered Tests (via executable)

The preferred way to run individual tests is to invoke the compiled test executable directly from artifacts\bin\. The executables use xUnit v3's built-in filter options — not the --filter flag.

Prerequisites

The test executables target a .NET preview runtime. The correct runtime version must be installed system-wide, or you must set DOTNET_ROOT to the repo-local .dotnet folder:

# From the repository root:
$env:DOTNET_ROOT = "$PWD\.dotnet"
$env:PATH = "$PWD\.dotnet;$env:PATH"

If the required .NET runtime is not installed, use the download-sdk skill to install it.

Note: The TFM in executable paths (e.g. net11.0) changes with each major .NET version. Check artifacts\bin\<ProjectName>\Debug\ for the actual TFM directory name.

Filter by method name (fully qualified)

& "artifacts\bin\System.Windows.Forms.Tests\Debug\net11.0-windows7.0\System.Windows.Forms.Tests.exe" `
  --filter-method "System.Windows.Forms.Tests.ButtonTests.Button_AutoSizeModeGetSet"

Filter by class

& "artifacts\bin\System.Windows.Forms.Tests\Debug\net11.0-windows7.0\System.Windows.Forms.Tests.exe" `
  --filter-class "System.Windows.Forms.Tests.ButtonTests"

Filter by namespace

& "artifacts\bin\System.Drawing.Common.Tests\Debug\net11.0\System.Drawing.Common.Tests.exe" `
  --filter-namespace "System.Drawing.Tests"

Wildcard matching

All filter options support * wildcards at the beginning and/or end:

# All test methods containing "AutoSize"
--filter-method "*AutoSize*"

# All classes ending with "ButtonTests"
--filter-class "*ButtonTests"

Filter by trait

--filter-trait "Category=Accessibility"

Exclude tests (negated filters)

--filter-not-method "*SlowTest*"
--filter-not-class "System.Windows.Forms.Tests.ClipboardTests"
--filter-not-trait "Category=Interactive"

Query filter language

For complex filtering, use --filter-query with xUnit's query filter language:

--filter-query "/*/*/ButtonTests/*"

Useful options

4b Running a Single Test via dotnet test (alternative)

dotnet test can also be used from the test project directory, but note that the --filter flag does not work with the Microsoft.Testing.Platform runner. To pass xUnit v3 filter options through dotnet test, use --:

pushd src\test\unit\System.Windows.Forms
dotnet test -- --filter-method "System.Windows.Forms.Tests.ButtonTests.Button_AutoSizeModeGetSet"

Note: If dotnet test --filter reports "Zero tests ran" with exit code 5, this is expected — switch to the executable approach in section 4 or use the -- separator.

5 Running Tests from Visual Studio

1. Launch via .\start-vs.cmd (ensures repo-local SDK is on PATH).
2. Open Test Explorer (Ctrl+E, T).
3. Run / debug tests as usual.

For common VS-specific issues see docs\testing-in-vs.md.

6 Test Project Layout

Each WinForms library has its own test projects:

src\
  test\
    unit\
      System.Windows.Forms\       ← System.Windows.Forms.Tests.csproj
  System.Drawing.Common\
    tests\                        ← System.Drawing.Common.Tests.csproj
  System.Windows.Forms.Primitives\
    tests\UnitTests\              ← ...Primitives.Tests.csproj
  System.Windows.Forms.Design\
    tests\UnitTests\              ← ...Design.Tests.csproj
  System.Windows.Forms.Analyzers\
    tests\UnitTests\              ← ...Analyzers.Tests.csproj
  ...

Test output (compiled executables) goes to:

artifacts\bin\<ProjectName>\Debug\<tfm>\<ProjectName>.exe

New test source files are auto-included (SDK-style project) — no .csproj edits needed.

7 Test Attributes & Categories

Theory data

Use [InlineData] or [MemberData] for parameterized tests. Avoid creating UI controls inside member-data methods — create them inside the test body instead.

8 Test Results & Troubleshooting

Parsing test results programmatically

TRX files are XML with namespace http://microsoft.com/schemas/VisualStudio/TeamTest/2010. To find failed tests:

Get-ChildItem "artifacts\TestResults\Debug\*.trx" | ForEach-Object {
    [xml]$trx = Get-Content $_.FullName
    $ns = @{t='http://microsoft.com/schemas/VisualStudio/TeamTest/2010'}
    $counters = Select-Xml -Xml $trx -XPath '//t:ResultSummary/t:Counters' -Namespace $ns |
        Select-Object -ExpandProperty Node
    if ([int]$counters.failed -gt 0) {
        Write-Host "=== $($_.BaseName) ($($counters.failed) failed) ==="
        Select-Xml -Xml $trx -XPath '//t:UnitTestResult[@outcome="Failed"]' -Namespace $ns |
            ForEach-Object { Write-Host "  FAIL: $($_.Node.testName)" }
    }
}

Common issues

• "Zero tests ran" with dotnet test --filter — the repo uses Microsoft.Testing.Platform, which does not support the --filter flag. Use the test executable directly with --filter-method / --filter-class (see section 4), or pass filters after -- separator.
• "Could not find testhost" / "testhost.deps.json not found" — vstest.console.exe and dotnet vstest cannot run these test assemblies. Use the test executable directly (section 4).
• "framework not found" when running test .exe — the required .NET preview runtime is not installed. Set DOTNET_ROOT to the repo-local .dotnet folder, or install the runtime using the download-sdk skill.
• Test runner crash — configure automatic memory-dump collection (Collecting User-Mode Dumps), then reproduce and inspect the dump in WinDbg.
• Flaky clipboard / drag-and-drop tests — ensure they are in the [Collection("Sequential")] collection so they don't run in parallel.
• VS test discovery fails — see docs\testing-in-vs.md.

Quick-Reference Command Cheat Sheet

# Full build + all unit tests
.\build.cmd -test

# Full build + all integration tests
.\build.cmd -integrationTest

# Single project tests (after initial build)
pushd src\test\unit\System.Windows.Forms
dotnet test

# --- Running individual tests via executable (preferred) ---

# Set up repo-local runtime (from repo root, if system runtime is not installed)
$env:DOTNET_ROOT = "$PWD\.dotnet"
$env:PATH = "$PWD\.dotnet;$env:PATH"

# Single test by fully-qualified method name
& "artifacts\bin\System.Windows.Forms.Tests\Debug\net11.0-windows7.0\System.Windows.Forms.Tests.exe" `
  --filter-method "System.Windows.Forms.Tests.ButtonTests.Button_AutoSizeModeGetSet"

# All tests in a class
& "artifacts\bin\System.Windows.Forms.Tests\Debug\net11.0-windows7.0\System.Windows.Forms.Tests.exe" `
  --filter-class "System.Windows.Forms.Tests.ButtonTests"

# Wildcard match on method name
& "artifacts\bin\System.Windows.Forms.Tests\Debug\net11.0-windows7.0\System.Windows.Forms.Tests.exe" `
  --filter-method "*AutoSize*"

# List all tests without running
& "artifacts\bin\System.Windows.Forms.Tests\Debug\net11.0-windows7.0\System.Windows.Forms.Tests.exe" `
  --list-tests