@include describe('_list-difference') {
  @include it('Properly reports items not in second list that are in first list') {
    @include assert-equal(
      _list-difference(
        (a b c z),
        (a b)
      ),
      (c z)
    );
  }

  @include it('Doesn\'t report items in second list not in first list') {
    @include assert-equal(
      _list-difference(
        (a b c),
        (z)
      ),
      (a b c)
    );
  }
}