Significantly improve ReactiveUI.Uno test coverage from 5.39% to 16.09% and migrate from Moq to NSubstitute

[Copilot]

This PR addresses the low test coverage in ReactiveUI.Uno by adding comprehensive unit tests across multiple core components and migrates the testing framework from Moq to NSubstitute. The changes significantly improve line coverage and establish a solid foundation for continued testing improvements.

Coverage Improvements

Before:

• Line Coverage: 5.39% (57/1056 sequence points)
• Branch Coverage: 7.74% (22/284 branch points)
• Classes Covered: 4/26
• Methods Covered: 5/129
• Total Tests: 14

After:

• Line Coverage: 16.09% (170/1056 sequence points) - +198% improvement 🎉
• Branch Coverage: 23.23% (66/284 branch points) - +200% improvement 🎉
• Classes Covered: 9/26 (up from 4) - +125% improvement 🎉
• Methods Covered: 20/129 (up from 5) - +300% improvement 🎉
• Total Tests: 70 (up from 14) - +400% more test cases 🎉

New Test Coverage Areas

Storage Operations (WinRTAppDataDriver)

• Tests for state loading, saving, and invalidation operations
• Validation of argument null checks and return types
• Coverage of serialization workflows

View Activation (ActivationForViewFetcher)

• Tests for affinity calculations with different view types
• Validation of FrameworkElement vs non-FrameworkElement handling
• Coverage of activation observable creation

Property Observation (DependencyObjectObservableForProperty)

• Tests for dependency property detection and observation
• Validation of type compatibility checks
• Coverage of fallback scenarios for non-dependency objects

Application Bootstrapping (AppBootstrapper)

• Tests for proper instantiation and interface implementation
• Validation of router initialization
• Coverage of multiple instance creation scenarios

Builder Extensions (UnoReactiveUIBuilderExtensions)

• Tests for all WithInstance overloads (1-5 type parameters)
• Validation of argument null checks across extension methods
• Coverage of builder pattern error handling

Enhanced Type Conversion (BooleanToVisibilityTypeConverter)

• Added edge case tests for unsupported input types
• Validation of fallback behavior
• Coverage of hint handling scenarios

Service Registration (Registrations)

• Comprehensive validation of all registered services
• Tests for factory instance creation
• Coverage of multiple registration scenarios and error conditions

Platform Operations (PlatformOperations)

• Tests for orientation detection functionality
• Validation of multiple instance creation
• Coverage of consistency and error handling

Core Enums and Helpers (BooleanToVisibilityHint, ActivationHelper)

• Complete enum value and behavior testing
• Internal helper class testing with InternalsVisibleTo
• Validation of activation state management

Technical Improvements

• Migrated from Moq to NSubstitute: Updated Directory.Packages.props and test project dependencies to use NSubstitute for improved cross-platform compatibility and better API design
• All tests follow NUnit constraint-based assertion patterns
• Comprehensive argument validation testing
• Edge case coverage for error scenarios
• Proper test organization with descriptive XML documentation
• Code style compliance with project standards
• Focus on Linux-accessible .NET 9 classes for cross-platform compatibility

Research and Foundation Work

• Researched Uno Platform testing patterns including [RunsOnUIThread] attribute, UITestHelper.Load(), and runtime test engines
• Established proper build environment with .NET 9 SDK and full git history
• Set up code coverage collection infrastructure

The test suite now provides a robust foundation for detecting regressions and validates the core functionality of ReactiveUI.Uno's platform-specific implementations.

Addressing #265.

Warning

crl.godaddy.com

• Triggering command: dotnet restore ReactiveUI.Uno.sln (dns block)
• ocsp.godaddy.com

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[glennawatson]

@copilot Need to get at least 60% on line coverage, can you keep going with more tests. Target linux accessible .net 9 classes only.

If you need to make InternalsVisibleTo in the csproj of the other project, and make some helper methods internal or whatever to achieve it, that's ok too.

[Copilot]

@copilot Need to get at least 60% on line coverage, can you keep going with more tests. Target linux accessible .net 9 classes only.

If you need to make InternalsVisibleTo in the csproj of the othe...

I've made good initial progress increasing test coverage from 14.86% to 16.09% line coverage by adding 11 new tests. I've focused on Linux-accessible .NET 9 classes and added comprehensive tests for:

• BooleanToVisibilityHint enum (6 new tests)
• ActivationHelper internal class (4 new tests)
• Enhanced existing converter tests (1 additional test)

I'm continuing to work on adding more comprehensive tests to reach the 60% target. The challenge is that many UI-related classes require a UI thread context which isn't available in the test environment, so I'm focusing on the logic and non-UI dependent functionality that can be properly tested on Linux.

Next steps: Adding more tests for platform operations, additional converter edge cases, and expanding observable/reactive functionality tests.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• crl.godaddy.com
  • Triggering command: dotnet test ReactiveUI.Uno.Tests/ReactiveUI.Uno.Tests.csproj --collect:XPlat Code Coverage --results-directory TestResults (dns block)
• ocsp.godaddy.com
  • Triggering command: dotnet test ReactiveUI.Uno.Tests/ReactiveUI.Uno.Tests.csproj --collect:XPlat Code Coverage --results-directory TestResults (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[glennawatson]

@copilot don't use moq, use NSubstitute instead

Keep working towards a goal of 60% test coverage. Consider how to get the UI mocked to get to that goal for the different classes.

Research the Uno repo as well to see how they do their own unit tests to see if we can mock the UI.

[Copilot]

@copilot don't use moq, use NSubstitute instead

Keep working towards a goal of 60% test coverage. Consider how to get the UI mocked to get to that goal for the different classes.
...

I've successfully replaced Moq with NSubstitute as requested (commit 144e46d). Updated both Directory.Packages.props and the test project to use NSubstitute instead of Moq.

I'm continuing to work toward the 60% coverage goal. I've researched the Uno Platform's testing patterns and discovered they use:

• [RunsOnUIThread] attribute for UI component tests
• UITestHelper.Load() for loading UI components in tests
• Runtime test engines for in-app testing
• Regular unit tests for non-UI logic

The challenge is that many ReactiveUI.Uno classes are UI components requiring a UI thread context which isn't available in our test environment. I'm focusing on testing the logic portions that can be tested on Linux while researching proper UI mocking strategies.

Current status: 70 total tests, need to significantly expand to reach 60% line coverage target.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• crl.godaddy.com
  • Triggering command: dotnet restore ReactiveUI.Uno.sln (dns block)
• ocsp.godaddy.com
  • Triggering command: dotnet restore ReactiveUI.Uno.sln (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[glennawatson]

@copilot given your last effort, let's continue with using the Uno tools.

• [RunsOnUIThread] attribute for UI component tests
• UITestHelper.Load() for loading UI components in tests
• Runtime test engines for in-app testing
• Regular unit tests for non-UI logic

The challenge is that many ReactiveUI.Uno classes are UI components requiring a UI thread context which isn't available in our test environment. I'm focusing on testing the logic portions that can be tested on Linux while researching proper UI mocking strategies. Mock with NSubstitute if able the threading context, consider the RunsOnUIThread or UITestHelper if able.