<!DOCTYPE html>
<html>
<head>
<link rel="author" title="Sammy Gill" href="mailto:sammy.gill@apple.com">
<link rel="help" href="https://drafts.csswg.org/css-box-4/#margin-trim-block">
<meta name="assert" content="border should protect the margins inside a nested block from trimming">
<style>
.trim {
    margin-trim: block;
}
container {
    display: block;
    width: min-content;
    outline: 1px solid blue;
}
item {
    display: block;
    inline-size: 50px;
    block-size: 25px;
}
.collapsed {
    block-size: 0px;
    margin-block: 14px;
}
.border {
    block-size: auto;
    border: 1px solid black;
    background-color: green;
    margin-block-end: 20px;
}
</style>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/check-layout-th.js"></script>
</head>
<body onload="checkLayout('.collapsed')">
    <div id="target">
        <container class="trim">
            <!-- Since this item has a border, the margins inside cannot collapse through
                 and should not be trimmed. However, its block-end border that was set
                 from the style should be trimmed. -->
            <item class="border">
                <item style="margin-block: 10px;"></item>
                <item data-offset-y="58" class="collapsed"></item>
            </item>
            <item data-offset-y="59" class="collapsed" style="margin-block: 5px 8px;"></item>
        </container>
    </div>
</body>
</html>
