Swift Asynchronous Testing

expectation.swift

class Fulfillment {
  var count: Int = 0
  func callAsFunction(count: Int = 1) {
    self.count += 1
  }
}

func expectation(
  _ comment: Comment,
  timeout: TimeInterval = 0.1,
  expectedCount: Int = 1,
  _ body: (Fulfillment) async -> Void
) async {
  let tries = Int(ceil(timeout / 0.01))
  let fulfillment = Fulfillment()
  for _ in 0..<tries {
    _ = await body(fulfillment)
    if fulfillment.count == expectedCount {
      return
    }
    try! await Task.sleep(for: .seconds(0.01))
  }
  if fulfillment.count == 0 {
    Issue.record("Fulfillment of: \"\(comment)\" never occurred")
  } else {
    Issue.record(
      """
        Fulfillment of: \"\(comment)\" failed \
        with count: \(fulfillment.count), \
        expected: \(expectedCount)
      """
    )
  }
}