JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box">
    <ul>
        <li><a href="#">test 1</a></li>
        <li><a href="#">test 2</a></li>
    </ul>
</div>

CSS

ul{
    list-style: none;
    padding: 0 0 10px;
    margin: 0;
    border-bottom: 5px solid green;
    overflow: hidden;
}

ul li{
    float: left;
    margin-left: 20px;
}

a{
    text-decoration: none;
    display: block;     
}

a:hover{
    border-bottom: 5px solid red;    
}