pkgs/markdown/test/original/fenced_code_block.unit

>>> issue #497
```
'foo'
```
<<<
<pre><code>'foo'
</code></pre>
>>> with basic metadata string
```dart meta
code
```

<<<
<pre data-metadata="meta"><code class="language-dart">code
</code></pre>
>>> with characters to escape
```dart title="main.dart"
code
```

<<<
<pre data-metadata="title=&quot;main.dart&quot;"><code class="language-dart">code
</code></pre>
>>> with HTML character reference
```dart &#124;
code
```

<<<
<pre data-metadata="|"><code class="language-dart">code
</code></pre>