swift-testing

Swift Testing Patterns

XCTest Basics

XCTest is Apple's foundational testing framework. Every test class inherits from XCTestCase and uses setUp/tearDown for lifecycle management.

import XCTest
@testable import MyApp

final class UserServiceTests: XCTestCase {
    var sut: UserService!
    var mockStore: MockUserStore!

    override func setUp() {
        super.setUp()
        mockStore = MockUserStore()
        sut = UserService(store: mockStore)
    }

    override func tearDown() {
        sut = nil
        mockStore = nil
        super.tearDown()
    }

    func testFetchUser_withValidID_returnsUser() {
        mockStore.stubbedUser = User(id: "1", name: "Alice")

        let user = sut.fetchUser(id: "1")

        XCTAssertNotNil(user)
        XCTAssertEqual(user?.name, "Alice")
    }

    func testFetchUser_withInvalidID_returnsNil() {
        mockStore.stubbedUser = nil

        let user = sut.fetchUser(id: "unknown")

        XCTAssertNil(user)
    }
}

Swift Testing Framework (Swift 5.9+)