swift-protocol-di-testing

The swift-protocol-di-testing skill provides a structured approach for making Swift code more testable by abstracting external dependencies behind well-defined protocols. By isolating file system, network, and API interactions into small, focused interfaces, developers can write deterministic tests without relying on real I/O operations or external systems. This approach addresses common challenges in Swift testing, such as handling asynchronous operations, working with sandboxed environments, and ensuring code behaves consistently across different environments and configurations.

Key features of this skill include defining small, single-responsibility protocols for each external dependency, creating default production implementations, and developing mock versions for testing purposes. It supports injecting dependencies into Swift actors and other types with default parameters, allowing production code to function normally while enabling test code to substitute mocks easily. The skill also emphasizes compatibility with Swift concurrency features and Sendable types, promoting safe and concurrent testable architecture. Example patterns include FileSystemProviding for container management, FileAccessorProviding for read/write operations, and BookmarkStorageProviding for persistent storage abstractions.

This skill is particularly useful for Swift developers building applications that interact with file systems, network services, or external APIs and who want reliable and reproducible test results. Target users include engineers designing modular architectures, QA engineers writing automated tests, and teams adopting Swift Testing frameworks for unit and integration testing. It is suitable for projects requiring cross-environment consistency, robust error handling tests, and maintainable testable code that can adapt to SwiftUI previews, production environments, and sandboxed contexts.