@include test-module('Sassdash') {
  $once: _once(test-square);
  $actual: _call($once, null, 2);

  @include test('should invoke func once') {
    @include assert-equal($actual, 4);
  }

  $actual: _call($once, null, 2);

  @include test('should invoke func once') {
    @include assert-equal($actual, null);
  }
}