providers.swift

// Define Provider Protocols
protocol NetworkProvider {
  var networkingService: NetworkServiceProtocol
}

protocol LoggingProvider {
  var loggerService: LoggerServiceProtocol
}

protocol ConfigurationProvider {
  var configService: ConfigServiceProtocol
}

// Create a Provider container for use in the app
class DefaultProvider: NetworkProvider, LoggingProvider, ConfigurationProvider {

  // singleton setup
  static var shared = ...

  let networkingService: NetworkServiceProtocol = {
    return NetworkService()
  }()

  let loggerService: LoggerServiceProtocol = {
    return LoggerService()
  }()

  let configService: ConfigServiceProtocol = {
    return ConfigService()
  }()
}

// Define a module's dependencies with protocol composition
class ExploreViewModel {
  typealias Dependencies = NetworkingProvider & LoggingProvider & ConfigurationProvider
  private let ctx: Dependencies

  init(ctx: Dependencies) {
    self.ctx = ctx
  }
}

let viewModel = ExploreViewModel(ctx: DefaultProvider.shared)

// Use a Mock provider for tests
class ViewModelMockProvider: NetworkProvider, LoggingProvider, ConfigurationProvider {
  let networkingService: NetworkServiceProtocol = {
    return MockNetworkService()
  }

  // ... etc
}

// ExploreViewModelTests.swift
let viewModel = ExploreViewModel(ctx: MockProvider())