JSFiddle - React, Tailwind, and code Playground

HTML

<div id="box">
    test<br />
    test<br />
    test<br />
    test<br />
    test<br />
    test<br />
    test<br />
    test<br />
    test<br />
    test<br />
    <hr id="bar">
</div>

CSS

#box {
    width: 200px;
    height: 150px;
    overflow-y: scroll;
}

#bar {
    width: 800px;
}