When editing your email, you have the option to view a personalized preview of your email. Under the Personalised Preview tab, you'll see what your email will look like for your test recipients.
On the top left, you can select an email address from the dropdown to check how the email will look for the recipient. You can only choose from the email addresses present in the test groups.
In the left sidebar, you see the database fields belonging to the contact. With this information, you can easily check if the personalised content of the email shows up the way you expect it to.