1) Create a new Confluence page.
2) Add the following as the content:

{composition-setup}
{composition-setup}

{deck:id=1}
{card:label=Card 1}
Card 1 content.
{card}
{card:label=Card 2}
Card 2 content.
{card}
{deck}

3) Switch to the Preview tab.

Nothing is shown in the page content, and several JavaScript errors are thrown.