Edit in JSFiddle

<h4>flex</h4>
<div class="flex">flex</div>
<span>test</span>
<h4>inline-flex</h4>
<div class="inline-flex">inline-flex</div>
<span>test</span>

.flex,
.inline-flex {
  width: 100px;
  height: 50px;
  border: 1px solid #000;
}

.flex {
  display: flex;
}

.inline-flex {
  display: inline-flex;
}