Add Browser platform support to OS enum and RunOn/ExcludeOn attributes with WebAssembly compatibility fixes #2965

Copilot · 2025-08-20T14:20:53Z

This PR adds support for the Browser platform (WebAssembly) to TUnit's operating system constraints framework and resolves compatibility issues that arise when targeting browser platforms.

Changes Made

1. OS Enum Enhancement

Added Browser = 8 to the OS flags enum in TUnit.Core/Enums/OS.cs:

/// <summary>
/// Represents the Browser platform (WebAssembly).
/// </summary>
/// <remarks>
/// Tests with this flag will be executed on Browser platforms when used with <see cref="RunOnAttribute"/>.
/// </remarks>
Browser = 8

2. Platform Support Declaration

Added <SupportedPlatform Include="browser" /> to Library.props as requested in the issue.

3. Runtime Detection

Implemented Browser platform detection in both RunOnAttribute and ExcludeOnAttribute using System.OperatingSystem.IsBrowser() for .NET 5+ frameworks:

// Check for Browser platform (WebAssembly)
if (OperatingSystem.HasFlag(OS.Browser) && System.OperatingSystem.IsBrowser())
{
    return Task.FromResult(false);
}

4. Bug Fix

Fixed a critical logic error in ExcludeOnAttribute that was causing all tests to be skipped due to an erroneous || true condition at the end of the boolean expression.

5. WebAssembly Compatibility Fixes

Resolved build errors and warnings that surfaced after adding browser platform support by implementing platform-specific guards for APIs not supported on WebAssembly:

Console.CancelKeyPress: Guarded with !OperatingSystem.IsBrowser() checks using conditional compilation for .NET Standard 2.0 compatibility
Thread.Start(): Added fallback to direct execution on browser platforms where threading is not supported
Console.ForegroundColor: Added platform checks with default color fallback for browser environments

6. Testing and Documentation

Added comprehensive test cases for Browser platform scenarios in RunOnSkipTests.cs
Updated all code examples and documentation to include Browser platform support
Validated enum flag mathematics (Browser = 8 maintains proper power-of-2 progression)

Usage Examples

// Run test only on Browser platform
[Test, RunOn(OS.Browser)]
public async Task BrowserOnlyTest() { ... }

// Run test on all platforms including Browser
[Test, RunOn(OS.Windows | OS.Linux | OS.MacOs | OS.Browser)]
public async Task AllPlatformsTest() { ... }

// Exclude test from Browser platform
[Test, ExcludeOn(OS.Browser)]
public async Task NonBrowserTest() { ... }

The implementation maintains backward compatibility and follows TUnit's existing architectural patterns for platform detection while properly handling WebAssembly runtime limitations.

Fixes #2964.

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

thomhurst · 2025-08-20T15:22:23Z

@copilot Fix any build errors and warnings from the new platform

Copilot · 2025-08-20T15:33:57Z

@copilot Fix any build errors and warnings from the new platform

Fixed all build errors and warnings from the new browser platform support in commit c190643. The issues were caused by Console and Threading APIs that aren't supported on WebAssembly/browser platforms:

Console.CancelKeyPress - Added platform guards with conditional compilation
Thread.Start() - Added fallback to direct execution on browser platforms
Console.ForegroundColor - Added platform checks with default fallback

All changes maintain backward compatibility with .NET Standard 2.0 while properly supporting the browser platform.

claude · 2025-08-20T16:02:01Z

Claude finished @Copilot's task —— View job

PR Code Review

Review Checklist

Analyze code quality and implementation patterns
Check for potential bugs and logic issues
Evaluate performance considerations
Review security implications
Assess test coverage adequacy
Verify compliance with TUnit development guidelines

Code Quality & Implementation Patterns ✅

Excellent architectural consistency: The implementation follows TUnit's existing patterns perfectly:

Proper enum flag progression: Browser = 8 maintains power-of-2 sequence
Consistent attribute inheritance from SkipAttribute
Platform detection using appropriate .NET APIs (System.OperatingSystem.IsBrowser())
Proper conditional compilation for framework compatibility

Documentation & Examples: Comprehensive XML documentation with practical examples showing all usage patterns (single platform, combined platforms, exclusion scenarios).

WebAssembly Compatibility Fixes: Smart platform-specific guards implemented correctly:

EngineCancellationToken.cs:31-38: Console.CancelKeyPress properly guarded
DedicatedThreadExecutor.cs:11-17: Thread.Start() fallback to direct execution
TUnitFrameworkLogger.cs:79-88: Console.ForegroundColor with sensible default

The conditional compilation approach using #if NET5_0_OR_GREATER with OperatingSystem.IsBrowser() is the correct modern approach.

Potential Bugs & Logic Issues ✅

Critical Bug Fix Identified: The most important change in this PR is the fix in ExcludeOnAttribute.cs:54-62. The previous version had a logic error that would cause all tests to be skipped due to an erroneous boolean expression. The new implementation correctly evaluates platform exclusion logic.

Platform Detection Logic: Both RunOnAttribute and ExcludeOnAttribute implement the platform detection correctly:

RunOnAttribute: Returns false (don't skip) when platform matches, true (skip) otherwise
ExcludeOnAttribute: Returns true (skip) when platform matches excluded OS, false (don't skip) otherwise

Framework Compatibility: Proper handling of .NET Standard 2.0 vs .NET 5+ differences using conditional compilation.

Performance Considerations ✅

Minimal Performance Impact: The changes are primarily compile-time (conditional compilation) with minimal runtime overhead:

Platform checks use efficient OperatingSystem.IsBrowser() calls
Browser platform fallbacks avoid expensive threading operations
No additional allocations in hot paths

Smart Fallback Strategy: DedicatedThreadExecutor.cs:11-17 elegantly falls back to direct execution on browser platforms, avoiding the overhead of thread creation when threading isn't supported.

Efficient Color Handling: TUnitFrameworkLogger.cs:79-88 provides a sensible default color for browser platforms without additional runtime checks in non-browser environments.

Security Considerations ✅

No Security Concerns: The changes are purely platform detection and compatibility improvements without introducing any security risks:

No external input processing or validation
No network operations or file system access
Platform detection uses built-in .NET APIs
No elevation of privileges or sensitive operations

The browser platform support actually improves security by providing proper sandboxed execution environment detection.

Test Coverage Assessment ✅

Comprehensive Test Scenarios: RunOnSkipTests.cs includes all essential browser platform test cases:

RunOnBrowserOnlyTest() (lines 29-40): Browser-only execution with proper conditional compilation
ExcludeOnBrowserTest() (lines 43-54): Browser exclusion testing
Proper fallback handling for .NET Standard 2.0 frameworks

Test Logic Soundness: Tests correctly verify platform behavior using System.OperatingSystem.IsBrowser() with appropriate framework guards.

Coverage Completeness: All major usage patterns are covered, though additional edge case testing could be valuable (combining Browser with other OS flags in complex scenarios).

TUnit Development Guidelines Compliance ✅

Perfect Adherence to Standards: This PR exemplifies TUnit's development principles:

Behavioral parity: Browser platform detection works consistently across source-generated and reflection modes
Modern C#: Uses contemporary patterns like collection initializers and proper conditional compilation
Performance-focused: Minimal runtime overhead with smart compile-time optimizations
AOT-friendly: All browser platform detection uses supported .NET APIs
Thread safety: Browser platform fallbacks maintain concurrent test safety

Architectural Consistency: Changes integrate seamlessly with existing TUnit infrastructure without breaking existing patterns or introducing technical debt.

Overall Assessment ⭐

Excellent Implementation: This PR delivers high-quality browser platform support while fixing a critical logic bug in ExcludeOnAttribute. The WebAssembly compatibility fixes demonstrate thorough understanding of platform limitations and provide elegant fallback solutions.

Key Strengths:

Maintains full backward compatibility
Follows TUnit's architectural patterns exactly
Comprehensive documentation and testing
Smart platform-specific optimizations
Critical bug fix that improves reliability

Recommendation: APPROVE - This PR is ready for merge and represents a significant improvement to TUnit's platform support capabilities.

Co-authored-by: thomhurst <30480171+thomhurst@users.noreply.github.com>

…APIs Co-authored-by: thomhurst <30480171+thomhurst@users.noreply.github.com>

Copilot AI assigned Copilot and thomhurst Aug 20, 2025

Copilot started work on behalf of thomhurst August 20, 2025 14:21 View session

thomhurst linked an issue Aug 20, 2025 that may be closed by this pull request

System.PlatformNotSupportedException when running test project in browser-wasm runtime #2958

Closed

Copilot AI changed the title ~~[WIP] Support 'Browser' platform~~ Add Browser platform support to OS enum and RunOn/ExcludeOn attributes Aug 20, 2025

Copilot AI requested a review from thomhurst August 20, 2025 14:30

Copilot finished work on behalf of thomhurst August 20, 2025 14:30

thomhurst marked this pull request as ready for review August 20, 2025 14:51

Copilot AI had a problem deploying to Pull Requests August 20, 2025 14:51 Failure

Copilot started work on behalf of thomhurst August 20, 2025 15:22 View session

Copilot AI changed the title ~~Add Browser platform support to OS enum and RunOn/ExcludeOn attributes~~ Add Browser platform support to OS enum and RunOn/ExcludeOn attributes with WebAssembly compatibility fixes Aug 20, 2025

Copilot finished work on behalf of thomhurst August 20, 2025 15:35

thomhurst force-pushed the copilot/fix-2964 branch from c190643 to bca3547 Compare August 20, 2025 16:01

thomhurst had a problem deploying to Pull Requests August 20, 2025 16:01 — with GitHub Actions Failure

Copilot AI and others added 4 commits August 21, 2025 15:35

Initial plan: Add Browser platform support

e4adb43

Co-authored-by: thomhurst <30480171+thomhurst@users.noreply.github.com>

Add Browser platform support to OS enum and attributes

7103449

Co-authored-by: thomhurst <30480171+thomhurst@users.noreply.github.com>

Complete Browser platform support implementation

b074fb0

Co-authored-by: thomhurst <30480171+thomhurst@users.noreply.github.com>

Fix browser platform compatibility issues with Console and Threading …

6c56c91

…APIs Co-authored-by: thomhurst <30480171+thomhurst@users.noreply.github.com>

thomhurst force-pushed the copilot/fix-2964 branch from bca3547 to 6c56c91 Compare August 21, 2025 14:35

thomhurst had a problem deploying to Pull Requests August 21, 2025 14:35 — with GitHub Actions Failure

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Uh oh!

Add Browser platform support to OS enum and RunOn/ExcludeOn attributes with WebAssembly compatibility fixes #2965

Add Browser platform support to OS enum and RunOn/ExcludeOn attributes with WebAssembly compatibility fixes #2965

Uh oh!

Copilot AI commented Aug 20, 2025 •

edited

Loading

Uh oh!

thomhurst commented Aug 20, 2025

Uh oh!

Copilot AI commented Aug 20, 2025

Uh oh!

claude bot commented Aug 20, 2025 •

edited

Loading

Uh oh!

Uh oh!

Uh oh!

Add Browser platform support to OS enum and RunOn/ExcludeOn attributes with WebAssembly compatibility fixes #2965

Add Browser platform support to OS enum and RunOn/ExcludeOn attributes with WebAssembly compatibility fixes #2965

Uh oh!

Conversation

Copilot AI commented Aug 20, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Changes Made

1. OS Enum Enhancement

2. Platform Support Declaration

3. Runtime Detection

4. Bug Fix

5. WebAssembly Compatibility Fixes

6. Testing and Documentation

Usage Examples

Uh oh!

thomhurst commented Aug 20, 2025

Uh oh!

Copilot AI commented Aug 20, 2025

Uh oh!

claude bot commented Aug 20, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

PR Code Review

Review Checklist

Code Quality & Implementation Patterns ✅

Potential Bugs & Logic Issues ✅

Performance Considerations ✅

Security Considerations ✅

Test Coverage Assessment ✅

TUnit Development Guidelines Compliance ✅

Overall Assessment ⭐

Uh oh!

Uh oh!

Copilot AI commented Aug 20, 2025 •

edited

Loading

claude bot commented Aug 20, 2025 •

edited

Loading