mozilla-release/layout/reftests/text/synthetic-bold-metrics-01.html

<!DOCTYPE html>
<html>
<head>
<style type="text/css">
@font-face {
  font-family: dejavu;
  src: url(../fonts/dejavu-sans/DejaVuSans.ttf);
}

p {
  font: 32px dejavu; /* family with only a single weight */
}

.test {
  color: white; /* hide the text, we're only comparing metrics */
  font-weight: bold; /* synthetic bold will be used */
}
</style>
</head>
<body>
<p>AbcdefghijklmnopqrstuvwxyZ</p>
<!-- the "test" span here uses synthetic bold, which should cause the following
     'Z' to appear further to the right -->
<p>A<span class="test">bcdefghijklmnopqrstuvwxy</span>Z</p>
</body>
</html>