JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div>
    <div>
      <span>TEST</span>
    </div>
    <div>
      <span>TEST</span>
    </div>
  </div>
</div>

CSS

.container {
    width: 100%;
    display: flex;
    border: 5px solid black;
}

.container > div {
    width: inherit;
    display: inline-flex;
    border: 5px solid red;
}

.container > div > div {
    border: 5px solid green;
    height: 50px;
    flex: 1;
}