pkgs/markdown/test/original/setext_headers.unit

>>> h1
text
===

<<<
<h1>text</h1>
>>> h2
text
---

<<<
<h2>text</h2>
>>> h1 on first line becomes text
===

<<<
<p>===</p>
>>> h2 on first line becomes text
-

<<<
<p>-</p>