@function filter_cond($item) { @return $item == 'a' or $item == 'b'; }

@include describe('_filter-function') {
  @include it('Properly filters the list using the provided function') {
    $input: a b c d a;
    $expected-output: a b a;
    @include assert-equal(
      _filter-function($input, filter_cond),
      $expected-output
    );
  }

  @include it('Nops empty lists') {
    $input: ();
    $expected-output: ();
    @include assert-equal(
      _filter-function($input, filter_cond),
      $expected-output
    );
  }
}