nt-size: 25px;
  font-family: Ahem;
  line-height: 1em;
}
.red {
  position: absolute;
  width: 100px;
  height: 100px;
  background: green;
  color: red;
  z-index: -1;
}
.test {
  color: green;
  width: 4ch;
  white-space: break-spaces;
  line-break: anywhere;
}
</style>
<body>
  <p>Test passes if there is a <strong>filled green square</strong> and <strong>no red</strong>.</p>
  <div class="red">XXXX<br>&nbsp;XXX<br>X X <br>X</div>
  <div class="test">XXXX&nbsp;XXXX X X</div>
</body>
