swift-mockable

swift-mockable provides a @Mockable macro that generates protocol mocks for tests.

• Generated mocks are emitted inside #if DEBUG.
• Generated names follow a predictable convention (<name>CallCount, <name>CallArgs, <name>Handler).
• resetMock() is generated to clear all tracking state.

Installation

Add the package:

dependencies: [
    .package(url: "https://github.com/yysskk/swift-mockable.git", from: "0.1.0")
]

Add Mockable to your target:

.target(
    name: "YourTarget",
    dependencies: ["Mockable"]
)

Quick Start

import Mockable

@Mockable
protocol UserService {
    func fetchUser(id: Int) async throws -> User
    func saveUser(_ user: User) async throws
    var currentUser: User? { get }
    var isLoggedIn: Bool { get set }
}

let mock = UserServiceMock()

mock.fetchUserHandler = { id in
    User(id: id, name: "Test User")
}

mock._currentUser = User(id: 1, name: "Current")
mock.isLoggedIn = true

let user = try await mock.fetchUser(id: 42)

#expect(user.id == 42)
#expect(mock.fetchUserCallCount == 1)
#expect(mock.fetchUserCallArgs == [42])

mock.resetMock()
#expect(mock.fetchUserCallCount == 0)

What Gets Generated

For each protocol requirement, @Mockable generates test-friendly members:

• Functions:
  • <method>CallCount
  • <method>CallArgs
  • <method>Handler
• Properties:
  • Backing storage for setup (for example _<property>)
  • Computed protocol-conforming property (property)
• Subscripts:
  • subscript<suffix>CallCount
  • subscript<suffix>CallArgs
  • subscript<suffix>Handler
  • subscript<suffix>SetHandler for get/set subscripts
• Utility:
  • resetMock()

Supported Features

• Access-level-aware generation (including private / fileprivate edge cases)
• Sync / async / throws methods
• Variadic parameters (captured as arrays)
• inout parameters with write-back support
• Generic methods (generic parameters are type-erased to Any in storage/handlers)
• Overloaded methods (unique suffixes are added to generated names when needed)
• Associated types (generated as typealias, using default type when available, otherwise Any)
• Static methods and static properties
• Get-only / get-set / optional properties
• Get-only / get-set subscripts
• #if / #elseif / #else conditional compilation inside protocols
• Protocol inheritance (child mock inherits from first parent mock when applicable)
• Sendable protocol support (@unchecked Sendable mock generation)
• Actor protocol support (actor mock generation with nonisolated helper members)

Behavioral Notes

• Return-value methods and get-only subscripts fatalError if their handler is not set.
• Void-return methods and subscript setters are no-op when handler is nil.
• resetMock() clears handlers, call counts, call arguments, and backing properties.
• For inherited protocols, resetMock() calls super.resetMock() before resetting child members.

Diagnostics and Limitations

• @Mockable can only be applied to protocols.
• @Mockable does not accept arguments.
• Unsupported protocol members (for example init) emit compile-time diagnostics.
• Static/class subscripts are not supported.
• For protocols with multiple parent protocols, the first parent is used as the mock superclass.

Documentation

• Docs index
• Advanced usage and naming rules

Requirements

• Swift 5.9, 5.10, and 6.2+
• macOS 10.15+ / iOS 13+ / tvOS 13+ / watchOS 6+
• MockableLock lock strategy:
  • iOS 18.0+ / macOS 15.0+ / tvOS 18.0+ / watchOS 11.0+: prefers Mutex (Synchronization)
  • Older OS versions: falls back to LegacyLock (NSLock-based)

License

MIT