present(value: null) (answer: Bool) { answer = false }
present(value: Uuid) (answer: Bool) {
 values = { value = 1 }
 values = put(values, value, 2)
 answer = uuid.toText(value) == "550e8400-e29b-41d4-a716-446655440000" and get(values, value) == 2 and length(values) == 1
}

verify() (answer: Bool) pure {
 answer = present(uuid.parse("550E8400-E29B-41D4-A716-446655440000")) and uuid.parse("550e8400e29b41d4a716446655440000") == null and uuid.parse("00000000-0000-0000-0000-00000000000-") == null
}

normalized(value: null) (text: Text?) pure { text = null }
normalized(value: Uuid) (text: Text?) pure { text = uuid.toText(value) }

roundtrip(text: Text) (value: Text?) pure { value = normalized(uuid.parse(text)) }

batchWithPending(values: List<Text>) (formatted: List<Text?>) {
 pending = run(dever.task.sleep(60000))
 formatted = each(roundtrip, values)
 stop(pending)
}

batchVerify() (answer: Bool) {
 values = ["550E8400-E29B-41D4-A716-446655440000", "invalid"]
 formatted = batchWithPending(values)
 empty = batchWithPending([])
 invalid = batchWithPending(["invalid"])
 answer = length(formatted) == 2 and first(formatted) == "550e8400-e29b-41d4-a716-446655440000" and length(invalid) == 1 and first(invalid) == null and length(empty) == 0 and values == ["550E8400-E29B-41D4-A716-446655440000", "invalid"]
}

taskVerify() (answer: Bool) {
 pending = run(roundtrip("550E8400-E29B-41D4-A716-446655440000"))
 value = wait(pending)
 answer = value == roundtrip("550E8400-E29B-41D4-A716-446655440000")
}