"First item in list is correct" tests head(). head() is expected to return the data associated with the list head rather than the node itself. Still figuring out the others...

Edit: oh okay. The naming of this method has left me completely fooled. This method is supposed to return just the data of the node at hand and not traverse the list all the way to its beginning ("first node", quoting the kata). At least this is what fixed tests in my case.