css/css-fonts/web-font-no-longer-accessible-when-stylesheet-removed.html

 <!DOCTYPE html>

<html>
    <head>
        <title>CSS fonts: Web fonts from removed stylsheets should not be accessible</title>
        <link rel="author" title="Martin Robinson" href="mrobinson@igalia.com">
        <link rel="match" href="web-font-no-longer-accessible-when-stylesheet-removed-ref.html">
        <link rel="help" href="https://drafts.csswg.org/css-fonts/#font-face-rule">
    </head>

    <body>
        <style id="web-font-stylesheet">
        @font-face {
            font-family: CustomFontFamily;
            src: url(/fonts/Ahem.ttf);
        }
        </style>

        <p>Test passes if the text below is not rendered with Ahem.</p>
        <p style="font-family: CustomFontFamily;">TEXT</p>

        <script>
            let styleTag = document.getElementById("web-font-stylesheet");
            styleTag.parentNode.removeChild(styleTag);
        </script>
    </body>

</html>