JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<button>
  <div class="container">
    <i class="fa fa-file-pdf-o" aria-hidden="true"></i>
    <span>TestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTestTest</span>
    <i class="fa fa-file-pdf-o" aria-hidden="true"></i>
  </div>
</button>

SCSS

body, button {
  max-width: 100px;
}

.container {
  width: 100%;
  display: flex;
  display: -ms-flexbox;
  
  span {
    flex: 1;
    -ms-flex: 1 0 auto;
    overflow: hidden;/**/
    white-space: nowrap;
    text-overflow: ellipsis;
    width: 50px;
  }
}