Add comprehensive unit test suite with 94 tests and 85% code coverage

[Blackbaud-PaulGibson]

Add comprehensive unit test suite with 94 tests and 85% code coverage

Summary

This PR adds a complete unit test suite for the SKY API Headless Data Sync application using xUnit and Moq, achieving 85% line coverage and 85% branch coverage with 94 tests. Additionally, the folder structure has been restructured to move the main project files to a src/ folder and test files to a tests/ folder, making both projects peer directories at the repository root level. Coverage report artifacts have been removed from source control following .NET community best practices.

Key Components Tested:

• AuthenticationService: OAuth token management and HTTP client configuration
• DataStorageService: Token storage, encryption/decryption, and file operations (with some limitations due to mocking challenges)
• ConstituentsService: API client HTTP requests and query parameter handling
• DataSyncService: Constituent data synchronization and error handling
• SyncApp: Command line argument parsing and timer orchestration
• Models: ListQueryParams, StorageData, and AppSettings validation

Structural Changes:

• Main project files moved from root → src/ directory
• Test files organized in tests/ directory
• Both projects are now peer folders with updated project references
• Coverage report files (38 files, 4,145 lines) removed from source control
• Updated .gitignore to exclude coverage artifacts

Review & Testing Checklist for Human

• 🔴 CRITICAL: Verify main application builds and runs correctly after folder restructuring - check that deployment scripts, CI/CD pipelines, and any build processes adapt to new src/ folder structure
• 🔴 CRITICAL: Test end-to-end application functionality to ensure no regressions were introduced during restructuring - run actual data sync operations
• 🔴 CRITICAL: Validate project references and build consistency - ensure all builds work correctly with the new ../src/skyapi-headless-data-sync.csproj reference
• 🟡 Validate test isolation: Run dotnet test and confirm no real API calls are made, no files created outside test directories, and no network dependencies
• 🟡 Review coverage gaps: Examine the 15% of uncovered code (including Program.cs) to ensure critical business logic and error paths aren't missed

Recommended Test Plan:

1. Clone branch and build main project: cd src && dotnet build
2. Run main application with sample configuration to verify functionality
3. Run all tests: cd tests && dotnet test
4. Generate coverage report locally: dotnet test --collect:"XPlat Code Coverage"
5. Test deployment/CI processes with new folder structure

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Diagram

%%{ init : { "theme" : "default" }}%%
flowchart TD
    Root["Repository Root"]:::context
    OldStructure["Old: Files at root level"]:::context
    NewSrc["src/<br/>Main Project Files"]:::minor-edit
    NewTests["tests/<br/>Test Project Files"]:::major-edit
    
    AuthService["src/Services/<br/>AuthenticationService.cs"]:::minor-edit
    DataStorage["src/Services/<br/>DataStorageService.cs"]:::minor-edit
    ConsService["src/Services/SkyApi/<br/>ConstituentsService.cs"]:::minor-edit
    SyncService["src/Services/DataSync/<br/>DataSyncService.cs"]:::minor-edit
    SyncApp["src/SyncApp.cs"]:::minor-edit
    
    AuthTests["tests/Services/<br/>AuthenticationServiceTests.cs"]:::major-edit
    DataTests["tests/Services/<br/>DataStorageServiceTests.cs"]:::major-edit
    ConsTests["tests/Services/SkyApi/<br/>ConstituentsServiceTests.cs"]:::major-edit
    SyncTests["tests/Services/DataSync/<br/>DataSyncServiceTests.cs"]:::major-edit
    AppTests["tests/SyncAppTests.cs"]:::major-edit
    
    Coverage["Coverage: 85% Line<br/>85% Branch<br/>94 Tests"]:::major-edit
    GitIgnore[".gitignore<br/>Coverage exclusions"]:::major-edit
    
    Root --> NewSrc
    Root --> NewTests
    Root --> GitIgnore
    
    NewSrc --> AuthService
    NewSrc --> DataStorage
    NewSrc --> ConsService
    NewSrc --> SyncService
    NewSrc --> SyncApp
    
    NewTests --> AuthTests
    NewTests --> DataTests
    NewTests --> ConsTests
    NewTests --> SyncTests
    NewTests --> AppTests
    
    AuthTests -.tests.-> AuthService
    DataTests -.tests.-> DataStorage
    ConsTests -.tests.-> ConsService
    SyncTests -.tests.-> SyncService
    AppTests -.tests.-> SyncApp
    
    NewTests --> Coverage
    
    subgraph Legend
        L1["Major Edit"]:::major-edit
        L2["Minor Edit"]:::minor-edit
        L3["Context/No Edit"]:::context
    end
    
    classDef major-edit fill:#90EE90
    classDef minor-edit fill:#87CEEB
    classDef context fill:#FFFFFF

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Notes

• ⚠️ Test isolation limitations: DataStorageService tests had to be simplified because data protection extension methods couldn't be properly mocked. The tests verify service instantiation and method calls but don't fully validate encryption/decryption logic.
• 📁 Folder restructuring risk: This is the highest risk change. Critical to verify that any CI/CD, deployment scripts, or build processes adapt to the new src/ folder structure.
• 📊 Coverage metrics: Generated using Coverlet and ReportGenerator tools. Reports can be regenerated locally but are no longer committed to source control.
• 🔒 All external dependencies mocked: HTTP clients, data protection providers, file system operations, and logging are mocked to ensure test isolation
• 🏗️ No main project code changes: Only moved files to new folder structure and added test exclusion to prevent test files from being compiled with the application
• 🚫 Coverage report cleanup: Removed 38 coverage report files (4,145 lines) from source control following .NET community best practices

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Link to Devin run: https://app.devin.ai/sessions/8804940a60164e04bf1b2a2f3b8431d1
Requested by: Paul Gibson (@Blackbaud-PaulGibson)

[Blackbaud-PaulGibson]

@devin-ai-integration restructure the folder hierarchy so that the skyapi-headless-data-sync.Tests project is at the same level as the main skyapi-headless-data-sync project. Under the root of the repo have a folder as the root for the main csproj and another folder for the test csproj so the two projects are peers.