css/css-values/random-item-unresolvable-argument.html

<!DOCTYPE html>
<title>CSS Values: random-item() with an item that is invalid at computed-value time</title>
<link rel="help" href="https://drafts.csswg.org/css-values-5/#funcdef-random-item">
<link rel="author" title="Joanne Pan" href="https://github.com/J0pan">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id="target"></div>
<script>

// When the selected item references a custom property that is guaranteed-invalid,
// the declaration is invalid at computed-value time and color falls back to its
// inherited/initial value, matching plain var() behavior.
test(() => {
    target.style.color = 'green';
    target.style.color = 'random-item(fixed 0, var(--missing), blue)';
    assert_equals(getComputedStyle(target).color, 'rgb(0, 0, 0)');
}, 'Selecting an item with an unresolvable var() is invalid at computed-value time');

// A different fixed index that selects a resolvable item still produces a value.
test(() => {
    target.style.color = 'green';
    target.style.color = 'random-item(fixed 0.999, var(--missing), rgb(1, 2, 3))';
    assert_equals(getComputedStyle(target).color, 'rgb(1, 2, 3)');
}, 'Selecting a resolvable item produces a value even when other items are unresolvable');

// A var() fallback inside the selected item is honored.
test(() => {
    target.style.color = 'green';
    target.style.color = 'random-item(fixed 0, var(--missing, rgb(4, 5, 6)), blue)';
    assert_equals(getComputedStyle(target).color, 'rgb(4, 5, 6)');
}, 'A var() fallback inside the selected item is used');

</script>