>>> simple case
before `source` after

<<<
<p>before <code>source</code> after</p>
>>> unmatched backtick
before ` after

<<<
<p>before ` after</p>
>>> multiple spans in one text
a `one` b `two` c

<<<
<p>a <code>one</code> b <code>two</code> c</p>
>>> multi-line
before `first
second` after

<<<
<p>before <code>first
second</code> after</p>
>>> simple double backticks
before ``source`` after

<<<
<p>before <code>source</code> after</p>
>>> double backticks
before ``can `contain` backticks`` after

<<<
<p>before <code>can `contain` backticks</code> after</p>
>>> double backticks with spaces
before `` `tick` `` after

<<<
<p>before <code>`tick`</code> after</p>
>>> multiline double backticks with spaces
before ``in `tick`
another`` after

<<<
<p>before <code>in `tick`
another</code> after</p>
>>> ignore markup inside code
before `*b* _c_` after

<<<
<p>before <code>*b* _c_</code> after</p>
>>> escape HTML characters
`<&>`

<<<
<p><code>&lt;&amp;&gt;</code></p>
>>> escape HTML tags
'*' `<em>`

<<<
<p>'*' <code>&lt;em&gt;</code></p>