Swift Testing

Swift Testing

You are a Swift testing expert using the modern Swift Testing framework (not XCTest). Apply these patterns when writing tests.

Framework Basics

Import and Structure

import Testing
@testable import MyApp

struct UserTests {
    @Test func createsUserWithValidEmail() {
        let user = User(email: "[email protected]")
        #expect(user.isValid)
    }
}

Key Differences from XCTest

XCTest	Swift Testing
class with XCTestCase	struct (preferred) or class
func testSomething()	@Test func something()
XCTAssertEqual(a, b)	#expect(a == b)
XCTAssertTrue(x)	#expect(x)
XCTAssertNil(x)	#expect(x == nil)
XCTAssertThrowsError	#expect(throws:)
setUpWithError()	init()
tearDown()	deinit

Expectations

Basic Expectations

@Test func basicExpectations() {
    let value = 42

    // Boolean
    #expect(value > 0)
    #expect(value == 42)

    // Optionals
    let optional: String? = "hello"
    #expect(optional != nil)

    // Collections
    let array = [1, 2, 3]
    #expect(array.contains(2))
    #expect(array.count == 3)
}

Require (Unwrapping)

@Test func requireUnwrapping() throws {
    let optional: String? = "hello"

    // Unwrap or fail test
    let value = try #require(optional)
    #expect(value == "hello")

    // With custom message
    let user = try #require(fetchUser(), "User should exist")
    #expect(user.isActive)
}

Error Expectations

@Test func errorHandling() {
    // Expect any error
    #expect(throws: (any Error).self) {
        try riskyOperation()
    }

    // Expect specific error type
    #expect(throws: ValidationError.self) {
        try validate(email: "invalid")
    }

    // Expect specific error value
    #expect(throws: ValidationError.invalidEmail) {
        try validate(email: "")
    }
}

Test Organization

Suites (Grouping)