@function test-filter-1($num, $args...) {
    @return $num % 2;
}
@include test-module('_filter') {
    @include test('should return elements predicate returns truthy for') {
        $actual: _filter(1 2 3, test-filter-1);
        $expected: 1 3;

        @include assert-equal($actual, $expected);
    }

    @include test('should be aliased') {
        $actual: _select(1 2 3, test-filter-1);
        $expected: _filter(1 2 3, test-filter-1);

        @include assert-equal($actual, $expected);
    }

    @include test('should work with shifted argument syntax for function') {
        $actual: _filter(black white yellow purple, lightness);

        @include assert-equal($actual, white yellow purple);
    }
}


@function test-filter-methods-1($value, $args...) {
  @return $value > 3;
}

@include test-module('filter methods') {
  @each $method-name in 'filter', 'reject' {
    $func: unquote('_#{$method-name}');
    $is-filter: $method-name == 'filter';


    @include test('#{$func} should work with a _pluck style predicate') {
      $maps: (('a': 0), ('a': 1));

      @include assert-lists-equal(
        _call($func, null, $maps, 'a'),
        (nth($maps, if($is-filter, 2, 1)),));
    }

    @include test('#{$func} should work with a _where style predicate') {
      $maps: (('a': 0), ('a': 1));

      @include assert-lists-equal(
        _call($func, null, $maps, nth($maps, 2)),
        (nth($maps, if($is-filter, 2, 1)),));
    }


    @include test('#{$func} should work in a lazy chain sequence') {
      $list: 1 2 3;

      $actual: _($list, _map test-square, $func test-filter-methods-1);

      @include assert-lists-equal(
        $actual,
        if($is-filter, 4 9, (1,)));
    }


    @include test('#{$func} should work in a lazy chain sequence (2)') {
      $map: ('a': 1, 'b': 2, 'c': 3);

      $actual: _(('a': 1, 'b': 4, 'c': 9), $func test-filter-methods-1);

      @include assert-lists-equal(
        $actual,
        if($is-filter, 4 9, (1,)));
    }
  }
}