// test_proceed should not be considered unit tests

function test_letexp() =
  let
    var a := 10
    var b := 20

    function add(x: int, y: int): int = x + y
    function sub(x: int, y: int): int = x - y
    function mul(x: int, y: int): int = x * y

    function test_proceed() =
      let
        function test_result(actual: int, expected: int) = assert actual = expected
      in
        (
          test_result(add(a, b), 30);
          test_result(sub(a, b), -10);
          test_result(mul(a, b), 200)
        )
      end
  in
    test_proceed()
  end