<!DOCTYPE html>
<style>
#target {
  width: 220px;
  height: 120px;
  overflow: scroll;
}
#inner {
  padding: 10px;
  box-shadow: 10px 10px green inset;
  height: 120px;
}
</style>
<div id="target">
  <div id="inner">
    Passes if green inset shadow is visible.
  </div>
</div>