@include test-module('_either') {
    @include test('should return the first value if it is truthy') {
        @include assert-equal(_either('abc', true), 'abc');
        @include assert-equal(_either('abc', 'def'), 'abc');
        @include assert-equal(_either((false: false), true), (false: false));
    }

    @include test('should return the second value if the first one is truthy, regardless of if the second value is truthy') {
        @each $value in $test-falsey {
            @include assert-equal(_either($value, 'abc'), 'abc');
            @include assert-equal(_either($value, false), false);
            @include assert-equal(_either($value, null), null);
        }
    }

    @include test('should work when only given one argument') {
        @include assert-equal(_either('abc'), 'abc');
    }

    @include test('should return null if only argument is falsey') {
        @each $value in $test-falsey {
            @include assert-equal(_either($value), null);
        }
    }

    @include test('should work with a predicate arg') {
        @include assert-equal(_either('', 'abc', _identity), '');
        @include assert-equal(_either(false, true, __is-falsey), false);
        @include assert-equal(_either(null, true, __is-falsey), null);
        @include assert-equal(_either('abc', 'def', _partial-right(_starts-with, 'q')), 'def');
    }

    @include test('should work with shifted argument syntax for predicate') {
        $list-1: 1 2 3;
        $list-2: 4 5 6;

        @include assert-equal(_either($list-1, $list-2, index 2), $list-1);
        @include assert-equal(_either($list-1, $list-2, index 5), $list-2);
        @include assert-equal(_either($list-1, $list-2, index 7), $list-2);
    }
}