let { TestEff, run, assert_eq, test, group, ? }  = import! std.test
let { lift } = import! std.effect.lift
let { (<|) } = import! std.function
let prelude  = import! std.prelude
let { Applicative, (*>), ? } = import! std.applicative
let int = import! std.int
let result @ { Result, ? } = import! std.result
let unit @ { ? } = import! std.unit
let { send, recv, channel } = import! std.channel


let { ? } = import! std.effect

let assert_recv channel expect : [Eq a] -> [Show a] -> _ -> Result () a -> _ =
    do x = lift <| recv channel
    assert_eq x expect

test "channel" <| \_ ->
    do { sender, receiver } = lift <| channel 0
    seq lift <| send sender 0
    seq lift <| send sender 1
    seq lift <| send sender 2
    seq assert_recv receiver (Ok 0)
    seq assert_recv receiver (Ok 1)
    assert_recv receiver (Ok 2)