Testing with Swift Testing and XCTest

Tests for Swift code

Swift has two testing frameworks. Swift Testing, introduced in 2024 with Xcode 16 and Swift 6, uses modern language features: import Testing, functions marked with @Test, expectations with the #expect(...) macro (which shows the values of sub-expressions when it fails) and #require(...) to stop a test when a precondition fails (for example unwrapping an optional). Tests can be parameterised with arguments:, grouped in suites (types marked @Suite), tagged, and run in parallel by default. XCTest is the long-standing framework (XCTestCase subclasses, XCTAssertEqual and friends) and is still required for UI tests and performance tests; the two can coexist in one project. Both support async tests. Use @testable import to test internal code. Make code testable with protocols for dependencies (a PaymentGateway protocol with a fake in tests), value-type models and pure functions. Run tests with Xcode's test navigator, swift test, or xcodebuild test in CI.

Swift Testing with parameterised cases and an async test

#expect shows values on failure; #require stops early.

import Testing
@testable import Pricing

@Suite("Shipping fees")
struct ShippingFeeTests {

    @Test("Fee depends on total and speed", arguments: [
        (totalPaise: 99_999, express: false, expected: 4_900),
        (totalPaise: 99_999, express: true,  expected: 9_900),
        (totalPaise: 100_000, express: true, expected: 0),
    ])
    func fee(totalPaise: Int, express: Bool, expected: Int) {
        #expect(ShippingCalculator().feePaise(total: totalPaise, express: express) == expected)
    }

    @Test func parsesAmount() throws {
        let money = try #require(Money(rupees: "499.00"))    // fails the test if nil
        #expect(money.paise == 49_900)
    }

    @Test func checkoutChargesOnce() async throws {
        let gateway = FakePaymentGateway()
        let checkout = Checkout(gateway: gateway)
        _ = try await checkout.pay(orderId: "o-1", amountPaise: 49_900)
        #expect(gateway.charges.count == 1)
    }
}

An inspector who shows the measurements

A plain assertion says "failed". #expect is an inspector who writes down every measurement: "fee was 9900, expected 4900, total was 99999", so you know immediately what went wrong.

त्वरित जाँच: In the Swift Testing framework, which macro checks a condition and reports sub-expression values on failure?

• XCTAssertTrue
• #expect
• @Test
• @testable