Magnolia 5.3 reached end of life on June 30, 2017. This branch is no longer supported, see End-of-life policy.
The Preview app allows you to test personalized content. You can impersonate a visitor to verify that the correct page variant is served. The impersonated visitor can be a persona or a mix of local traits. The Preview app looks just like the preview in the Pages app but it has a sidebar for selecting the persona and traits.