You'll likely want to preview your survey before publishing it so you can test it out and confirm everything is working correctly. You can preview using a small code snippet or with a custom URL scheme in iOS.
Previewing using code
Previewing using code is easier during initial development to confirm you've installed everything correctly.
In the "Preview & Publish" tab select your platform under the Test Your Survey heading and copy the code. This makes use of the preview method which will ensure the survey is returned once the event your survey is targeting is fired.
Previewing using a custom URL scheme on iOS
Previewing using the custom URL scheme makes it easier to test on actual devices and for those without access to xcode.
Once set up you can scan the QR code on the "Preview & Publish" tab of your survey which will open your app allowing you to preview the survey once the event you're targeting has fired.