Unit Testing

Asynchronous

// Setup
var sut: URLSession!

override func setUpWithError() throws {
  try super.setUpWithError()
  sut = URLSession(configuration: .default)
}

override func tearDownWithError() throws {
  sut = nil
  try super.tearDownWithError()
}

// Next, add this asynchronous test:

// Asynchronous test: success fast, failure slow
func testValidApiCallGetsHTTPStatusCode200() throws {
  // given
  let urlString = 
    "http://www.randomnumberapi.com/api/v1.0/random?min=0&max=100&count=1"
  let url = URL(string: urlString)!
  // 1
  let promise = expectation(description: "Status code: 200")

  // when
  let dataTask = sut.dataTask(with: url) { _, response, error in
    // then
    if let error = error {
      XCTFail("Error: \(error.localizedDescription)")
      return
    } else if let statusCode = (response as? HTTPURLResponse)?.statusCode {
      if statusCode == 200 {
        // 2
        promise.fulfill()
      } else {
        XCTFail("Status code: \(statusCode)")
      }
    }
  }
  dataTask.resume()
  // 3
  wait(for: [promise], timeout: 5)
}

func testApiCallCompletes() throws {
  // given
  let urlString = "http://www.randomnumberapi.com/test"
  let url = URL(string: urlString)!
  let promise = expectation(description: "Completion handler invoked")
  var statusCode: Int?
  var responseError: Error?

  // when
  let dataTask = sut.dataTask(with: url) { _, response, error in
    statusCode = (response as? HTTPURLResponse)?.statusCode
    responseError = error
    promise.fulfill()
  }
  dataTask.resume()
  wait(for: [promise], timeout: 5)

  // then
  XCTAssertNil(responseError)
  XCTAssertEqual(statusCode, 200)
}

UI Testing in Xcode

Use Record button to generate testing code.

Performance Testing

func testScoreIsComputedPerformance() {
  measure(
    metrics: [
      XCTClockMetric(), 
      XCTCPUMetric(),
      XCTStorageMetric(), 
      XCTMemoryMetric()
    ]
  ) {
    sut.check(guess: 100)
  }
}

Enabling Code Coverage