test Test:
    let list1 = [ 1 ]
    let list2 = [ 2, 3 ]
    let empty = [  ]

    node n

    let c1 = concat [[ 1 ]]
    for i in c1:
        shell on n:
            echo "c1 $i"
    local:
        shell on n:
            echo "c1-end"

    let c2 = concat [[ 1 ], [], empty]
    for i in c2:
        shell on n:
            echo "c2 $i"
    local:
        shell on n:
            echo "c2-end"

    let c3 = concat [ list1, list2, [ 6, 5 ], list2 ]
    for i in c3:
        shell on n:
            echo "c3 $i"
    local:
        shell on n:
            echo "c3-end"