feat(tests): implement testing strategy for MCP tools

[CalvinAllen]

Summary

Implement a comprehensive testing strategy for the 17 MCP tools exposed by the VS-VSMCP extension.

Current State

• 17 MCP tools across 3 categories (Solution, Document, Build)
• No existing test projects or test coverage
• Three-tier architecture: MCP Client → Server Process (named pipes) → VS Extension

Proposed Test Projects

Project	Purpose	Framework
CodingWithCalvin.VSMCP.Server.Tests	Unit tests for server tools	xUnit
CodingWithCalvin.VSMCP.Shared.Tests	Model and contract tests	xUnit
CodingWithCalvin.VSMCP.Integration.Tests	RPC pipe communication tests	xUnit

Testing Layers

Unit Tests (High Priority)

• Server Tools: Mock IVisualStudioRpc interface, verify tool methods handle parameters correctly and return expected results
• Shared Models: JSON serialization/deserialization round-trips for all DTOs
• Tool Discovery: Reflection-based tool enumeration from [McpServerTool] attributes

Integration Tests (Medium Priority)

• RPC client/server named pipe communication (without VS)
• Connection lifecycle (connect, disconnect, reconnect)
• JSON-RPC message format validation
• Error handling and timeout scenarios

E2E Tests (Manual)

• Full flow with Visual Studio (requires experimental instance)
• Claude Desktop integration testing

Tools to Cover

Solution Tools (5)

• solution_info
• solution_open
• solution_close
• project_list
• project_info

Document Tools (11)

• document_list
• document_active
• document_open
• document_close
• document_read
• document_write
• selection_get
• selection_set
• editor_insert
• editor_replace
• editor_find
• editor_goto_line

Build Tools (5)

• build_solution
• build_project
• clean_solution
• build_cancel
• build_status

Acceptance Criteria

• Create test projects with xUnit framework
• Implement unit tests for all 17 tools with mocked RPC
• Implement model serialization tests
• Implement RPC integration tests
• Add test step to CI/CD workflow (.github/workflows/build.yml)
• Achieve meaningful code coverage for server and shared projects