How to get the super user in a functional test?
Looking into BrowserTestBase I accidentally found $this-&gt;rootUser-&gt;name and $this-&gt;rootUser-&gt;pass_raw last week. These are being used in installParameters(). I have not tested it, but I suppose you should be able to use those in other functions as well. 

rootUser appears to be a full AccountInterface object, so getName() and other methods should work as well..