<!DOCTYPE html>
<style>
#container {
position: fixed;
top: 200px;
left: 100px;
}
#block {
position: relative;
width: 100px;
height: 100px;
top: 50px;
background-color: green;
}
</style>
<div id="container">
<div id="block"></div>
</div>
This test passes if the green block stays at the same place after repaint.