Implement Unit Test Infrastructure with SDK Abstraction Patterns

[Copilot]

This PR establishes the foundation for comprehensive unit testing in PepperDash Essentials by creating a modern test infrastructure and demonstrating SDK abstraction patterns.

Problem Solved

The codebase previously had no unit testing infrastructure, making it difficult to:

• Test business logic independently of Crestron SDK dependencies
• Catch regressions early in development
• Refactor code safely
• Maintain code quality standards

Implementation

🧪 Test Infrastructure

• New test project using .NET 8 with xUnit, Moq, and code coverage
• 10 comprehensive unit tests demonstrating best practices
• CI integration via GitHub Actions for automated test execution
• Solution integration with proper project structure

🔧 Abstraction Pattern Demonstration

Created testable interfaces for common SDK dependencies:

public interface IThreadService
{
    void Sleep(int milliseconds);
    object CreateAndStartThread(Func<object, object> threadFunction, object parameter);
    bool IsThreadRunning(object thread);
}

public interface ILogger  
{
    void LogDebug(object source, string message, params object[] args);
}

TestableActionSequence shows how to refactor existing components:

• Dependency injection for SDK abstractions
• Pure business logic testing
• Comprehensive test coverage (constructor validation, state management, threading logic)

📚 Documentation & Guidelines

• Complete testing guide (docs/testing/README.md) with patterns and best practices
• Quick start guide (docs/testing/QuickStart.md) for developers
• CI workflow for automated testing on PRs

🎯 Test Results

Test Run Successful.
Total tests: 10
     Passed: 10
 Total time: 0.7954 Seconds

Benefits

1. Immediate Value: Working test infrastructure ready for expansion
2. Risk Reduction: Safer refactoring and feature development
3. Quality Improvement: Early detection of bugs and regressions
4. Developer Experience: Fast feedback loops and better debugging
5. Future-Proofing: Foundation for eventual .NET 8 migration

Minimal Impact Approach

This implementation:

• ✅ Zero breaking changes - existing code unmodified
• ✅ Plugin compatibility - no interface changes
• ✅ Incremental adoption - teams can apply patterns gradually
• ✅ Modern tooling - .NET 8 for tests while keeping .NET Framework 4.7.2 for main code

Next Steps

Teams can now:

1. Apply abstraction patterns to critical components
2. Write tests for existing business logic
3. Use CI to catch issues early
4. Build confidence for future modernization efforts

Fixes #1297.

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[ngenovese11]

@copilot could you attempt to refactor starting from the net8-updates branch? I think that we want to create a new net8 class library with only a dependency on newtonsoft, and that's where our abstractions will live (lets call the class lib PepperDash.Essentials.Contracts for now)

[Copilot]

@copilot could you attempt to refactor starting from the net8-updates branch? I think that we want to create a new net8 class library with only a dependency on newtonsoft, and that's where our abstra...

I've successfully refactored the testing infrastructure starting from the net8-updates branch as requested.

Created the new PepperDash.Essentials.Contracts .NET 8 class library with only Newtonsoft.Json dependency. The library contains:

Abstractions moved from test project:

• ILogger - for logging operations
• IThreadService - for thread management
• IQueue<T> - for queue operations

Components:

• TestableActionSequence - demonstrates usage patterns

Testing: Comprehensive unit tests validate the abstractions work correctly (3/3 tests passing)

Documentation: Created usage guide at docs/contracts/README.md

All projects build successfully and integrate cleanly with the existing solution structure. This provides a foundation for gradual adoption of testable patterns across the codebase.