Асинхронные тесты и измерение производительности

final class FetcherTests: XCTestCase {
  func testFetchReturnsUser() async throws {
    let user = try await UserService().fetchUser(id: 1)
    XCTAssertEqual(user.name, "Alice")
  }
}

override func setUp() async throws {
  try await super.setUp()
  sut = await AsyncService.make()
}

func testCallback() {
  let exp = expectation(description: "data received")
  service.fetchWithCallback { data in
    XCTAssertNotNil(data)
    exp.fulfill()
  }
  wait(for: [exp], timeout: 5.0)
}

let noCall = expectation(description: "should not fire")
noCall.isInverted = true
cancelledTask.onComplete { noCall.fulfill() }
wait(for: [noCall], timeout: 1.0)

func testSortPerformance() {
  let data = Array(0..<10_000).shuffled()
  measure {
    _ = data.sorted()
  }
}

func testParsePerformance() {
  let options = XCTMeasureOptions()
  options.iterationCount = 5
  measure(options: options) {
    _ = try? JSONDecoder().decode([Item].self, from: largeJSON)
  }
}

func testAsyncFetchPerformance() {
  measure {
    let exp = expectation(description: "done")
    Task {
      _ = try? await service.fetchAll()
      exp.fulfill()
    }
    wait(for: [exp], timeout: 10)
  }
}

// Xcode: click the grey icon next to the measure test
// → "Set Baseline" to record the current average
// Subsequent runs compare against the baseline

actor Counter { var value = 0; func increment() { value += 1 } }
final class CounterTests: XCTestCase {
  func testIncrement() async {
    let counter = Counter()
    await counter.increment()
    let val = await counter.value
    XCTAssertEqual(val, 1)
  }
}

import Testing

@Suite struct MathTests {
  @Test func addition() {
    #expect(2 + 2 == 4)
  }
}

import XCTest
import Testing
// Legacy XCTestCase tests alongside @Test functions
// Both run when the test target is executed