ght: 200px;
}
.target {
  width: 100px;
  height: 150px;
}
.target::before {
  display: block;
  content: "";
  width: 100px;
  height: 50px;
}
</style>

<body>
<script>
test_composition({
  property: 'height',
  underlying: 'fit-content', /* 50px */
  addFrom: '100px',
  addTo: '200px',
}, [
  {at: -0.3, expect: '120px'},
  {at: 0, expect: '150px'},
  {at: 0.5, expect: '200px'},
  {at: 1, expect: '250px'},
  {at: 1.5, expect: '300px'},
]);

test_composition({
  property: 'height',
  underlying: 'fit-conten