How can I test what an email I've created will look like?

When you configure the content for an automatic email you can see a preview of how the email will look by selecting Preview Email beside the version you wish to see:

If you have changed any of the content of the email, and that’s what you are wanting to preview, you must select save changes before trying to preview the email.

Alternatively, to see how the email looks, you could perform the action on your website or in the management system that triggers the email to be sent. For example, if you want to see an order status email that you have configured you could create an order in your account which contains your own email address. Then change the order status for the order to the one for the email you want to see. The order status email will then be sent to you so you can see how it looks.