<style>
.container {
  width: 250px;
  color: transparent;
}

.float {
  margin-left: -1px;
  float: left;
}

.float:nth-child(1) {
  background-color: green;
  width: 30px;
  height: 20px;
}

.float:nth-child(2) {
  background-color: blue;
  width: 100px;
  height: 80px;
}

.float:nth-child(3) {
  background-color: grey;
  width: 30px;
  height: 20px;
}

.float:nth-child(4) {
  background-color: red;
  width: 100px;
  height: 20px;
}

.float:nth-child(5) {
  background-color: cyan;
  width: 5px;
  height: 20px;
}

</style>
<div class=container>
  <div class=float></div>
  <div class=float></div>
  <div class=float></div>
  <div class=float></div>
  <div class=float></div>
  PASS if floats don't overlap
</div>