How do you write unit tests in Swift? Compare Swift Testing and XCTest.

import Testing
@testable import Shop

@Suite("Cart")
struct CartTests {
    @Test func emptyCartHasZeroTotal() {
        let cart = Cart()
        #expect(cart.total == 0)
    }

    @Test func addingItemsUpdatesTotal() throws {
        var cart = Cart()
        try cart.add(Item(price: 10), quantity: 2)
        #expect(cart.total == 20)
        #expect(cart.items.count == 1)
    }
}

@Test func decodesFirstProduct() throws {
    let products = try JSONDecoder().decode([Product].self, from: fixture)
    let first = try #require(products.first) // unwraps or fails and stops
    #expect(first.name == "Lamp")
}

@Test(arguments: [
    ("a@b.com", true),
    ("no-at-sign", false),
    ("", false)
])
func validatesEmail(input: String, isValid: Bool) {
    #expect(EmailValidator.isValid(input) == isValid)
}

@Test func loadsProfile() async throws {
    let model = ProfileModel(api: FakeAPI(user: .sample))
    try await model.load()
    #expect(model.name == "Ana")
}

@Test func rejectsNegativeQuantity() {
    var cart = Cart()
    #expect(throws: CartError.invalidQuantity) {
        try cart.add(Item(price: 5), quantity: -1)
    }
}

@Test func notifiesOnSave() async {
    await confirmation("saved") { saved in
        let store = Store(onSave: { saved() })
        await store.save()
    }
}

@Test(.disabled("Flaky on CI")) func syncs() async {}
@Test(.tags(.networking), .timeLimit(.minutes(1))) func downloads() async {}
@Suite(.serialized) struct DatabaseTests {} // run one by one

import XCTest
@testable import Shop

final class CartXCTests: XCTestCase {
    var cart: Cart!

    override func setUp() {
        super.setUp()
        cart = Cart()
    }

    func testAddingItemsUpdatesTotal() throws {
        try cart.add(Item(price: 10), quantity: 2)
        XCTAssertEqual(cart.total, 20)
    }

    func testLoadsProfile() async throws {
        let model = ProfileModel(api: FakeAPI(user: .sample))
        try await model.load()
        XCTAssertEqual(model.name, "Ana")
    }
}