type ValueResult { Ready(value: Int)
  error Failed(message: Text) }

work(delay: Int, number: Int) (value: Int) { dever.task.sleep(delay)
 value = number }

fallback() (value: Int) { value = 7 }

bad(delay: Int) (value: Int) { dever.task.sleep(delay)
 fail(ValueResult.Failed("worker")) }

fallbackFault() (value: Int) { fail(ValueResult.Failed("fallback")) }

nothing() (value: Int?) { value = null }

nullableFallback() (value: Int?) { value = 9 }

pair(delay: Int) (first: Int, second: Text) { dever.task.sleep(delay)
 first = 4
 second = "pair" }

pairFallback() (first: Int, second: Text) { first = 7
 second = "fallback" }

empty() () {}

duration() (value: Int) { dever.task.sleep(0)
 value = 10000 }

badDuration() (value: Int) { dever.task.sleep(0)
 fail(ValueResult.Failed("argument")) }

timeoutFault() (value: Int) { value = timeout(run(bad(0)), 10000, fallbackFault) }

raceFault() (value: Int) { value = race(run(bad(0)), run(work(60000, 3))) }

invalidTimeout() () { timeout(run(dever.task.sleep(60000)), 0, empty) }

argumentFault() (value: Int) { value = timeout(run(work(60000, 3)), badDuration(), fallback) }

raceArgumentFault() (value: Int) { value = race(run(work(60000, 1)), run(work(badDuration(), 2))) }

verify() (answer: Bool) {
  ready = timeout(run(work(0, 1)), 10000, fallback)
  expired = timeout(run(work(60000, 2)), 1, fallback)
  nullable = timeout(run(nothing()), 10000, nullableFallback)
  evaluated = timeout(run(work(0, 3)), duration(), fallback)
  pair_value = timeout(run(pair(0)), 10000, pairFallback)
  pair_expired = timeout(run(pair(60000)), 1, pairFallback)
  pair_winner = race(run(pair(60000)), run(pair(0)))
  winner = race(run(work(60000, 1)), run(work(60000, 2)), run(work(0, 3)))
  timeout(run(dever.task.sleep(0)), 10000, empty)
  timeout(run(dever.task.sleep(60000)), 1, empty)
  race(run(dever.task.sleep(60000)), run(dever.task.sleep(0)))
  answer = ready == 1 and expired == 7 and nullable == null and evaluated == 3 and pair_value.first == 4 and pair_value.second == "pair" and pair_expired.first == 7 and pair_expired.second == "fallback" and pair_winner.first == 4 and pair_winner.second == "pair" and winner == 3
}