showdownjs/test/cases/emphasis.html

<p><em>single asterisks</em></p>

<p><em>single underscores</em></p>

<p><strong>double asterisks</strong></p>

<p><strong>double underscores</strong></p>

<p>text <em>with italic sentence</em> in middle</p>

<p>text <strong>with bold sentence</strong> in middle</p>

<p>text with <strong>bold text that
  spans across multiple</strong> lines</p>

<p>underscored_word</p>

<p>doubleunderscore__word</p>

<p>asterix*word</p>

<p>doubleasterix**word</p>

<p>line with_underscored word</p>

<p>line with__doubleunderscored word</p>

<p>line with*asterixed word</p>

<p>line with**doubleasterixed word</p>

<p>some line<em>with</em>inner underscores</p>

<p>some line<strong>with</strong>inner double underscores</p>

<p>some line<em>with</em>inner asterixs</p>

<p>some line<strong>with</strong>inner double asterixs</p>

<p>another line with just _one underscore</p>

<p>another line with just __one double underscore</p>

<p>another line with just *one asterix</p>

<p>another line with just **one double asterix</p>

<p>a sentence with<em>underscore and another</em>underscore</p>

<p>a sentence with<strong>doubleunderscore and another</strong>doubleunderscore</p>

<p>a sentence with<em>asterix and another</em>asterix</p>

<p>a sentence with<strong>doubleasterix and another</strong>doubleasterix</p>

<p>escaped word_with_underscores</p>

<p>escaped word__with__double underscores</p>

<p>escaped word<em>_with_</em>single italic underscore</p>

<p>escaped word*with*asterixs</p>

<p>escaped word**with**asterixs</p>

<p>escaped word<strong>*with*</strong>bold asterixs</p>