chromium/third_party/blink/web_tests/external/wpt/css/css-syntax/url-whitespace-consumption.html

<!doctype html>
<title>url whitespace consumption</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>

.foo {}

</style>

<meta name=author title="Tab Atkins-Bittner">
<link rel=help href="https://drafts.csswg.org/css-syntax/#consume-ident-like-token">

<script>

function roundTripUrl(input) {
    const rule = document.styleSheets[0].cssRules[0].style;
    const fallback = 'url("fallback")';
    rule.setProperty("background-image", fallback);
    rule.setProperty("background-image", input);
    const value = rule.getPropertyValue("background-image");
    if(value == fallback) return false;
    return value;
}

test(()=>{
    assert_equals(roundTripUrl('url("foo")'), 'url("foo")');
    assert_equals(roundTripUrl('url( "foo")'), 'url("foo")');
    assert_equals(roundTripUrl('url("foo" )'), 'url("foo")');
}, "whitespace is optional between url( token and the string token");

</script>