Position fixed but for specific container only

Question

I'm trying to set position fixed of a div inside of parent div.

Like for example:

.parent-div {
  height: 500px;
}

.fixed {
  position: fixed;
}

<div class="container parent-div">
  <div class="container fixed">
    Test
  </div>
</div>

Goal is, if user scroll fixed class will only be sticky they are currently scrolling on parent-div