There are two tests you can do with the HREFlang Testing Tool
Check In-Page HREFLang XML Tags
If you have HREFLang XML tags in the <head> tag of each of your pages you can add one of the pages into the URL box of the tool and it will test to make sure that they are correct. If you get any errors you can review them and consult our help section if there are any questions.
Check a Blended HREFLang XML Site Map
If you have a smaller site and have added HREFLang configurations to your XML site map you can put the URL of the site map in the tool and we will test it. Unfortunately, this will not test across XML site maps. If you wish to do this please subscribe to HREFlang Builder.