<!doctype html>
<html>
<head>
<script src="../../resources/js-test-pre.js"></script>
<style>
html {
    background-color:white;
}
html:nth-last-child(1) {
    background-color:rgb(1, 2, 3);
}
html:nth-last-child(n) {
    background-color:rgb(1, 2, 3);
}
html:nth-last-child(n+1) {
    background-color:rgb(1, 2, 3);
}

:root:nth-last-child(1) {
    background-color:rgb(1, 2, 3);
}
:root:nth-last-child(n) {
    background-color:rgb(1, 2, 3);
}
:root:nth-last-child(n+1) {
    background-color:rgb(1, 2, 3);
}

svg:nth-last-child(n) {
    background-color:rgb(1, 2, 3);
}
svg:root {
    background-color:rgb(4, 5, 6);
}
</style>
</head>
<body>
    <div style="display:none">
        <svg><g></g></svg>
    </div>
</body>
<script>
description('Verify the nth-last-child() pseudo class matcher always test for the parent element. Some :nth-last-child pseudo selectors can skip counting the siblings, but they should never skip the parent check.');

shouldBe('document.querySelectorAll("html:nth-last-child(1)").length', '0');
shouldBe('document.querySelectorAll("html:nth-last-child(n)").length', '0');
shouldBe('document.querySelectorAll("html:nth-last-child(n+1)").length', '0');
shouldBe('document.querySelectorAll(":root:nth-last-child(1)").length', '0');
shouldBe('document.querySelectorAll(":root:nth-last-child(n)").length', '0');
shouldBe('document.querySelectorAll(":root:nth-last-child(n+1)").length', '0');
shouldBeEqualToString('getComputedStyle(document.documentElement).backgroundColor', 'rgb(255, 255, 255)');

// This svg document is not the root, ":root" should not match anything, nth-last-child should work.
shouldBe('document.querySelectorAll("svg:root").length', '0');
shouldBe('document.querySelectorAll("svg:nth-last-child(1)").length', '1');
shouldBe('document.querySelectorAll("svg:nth-last-child(n)").length', '1');
shouldBeEqualToString('getComputedStyle(document.querySelector("svg")).backgroundColor', 'rgb(1, 2, 3)');
</script>
<script src="../../resources/js-test-post.js"></script>
</html>