@include test('lt(..)') {
  $tests: (
    '3.2.1': true,
    '1.2.3': false,
    '0.1.2': false,
  );

  @each $test, $expect in $tests {
    @include assert-equal(lt('1.2.3', $test), $expect, 'Returns whether v1 is letter than v2.');
  }
}