We need to be able to take a placement test at the end of all the lessons
It would be nice if we could take a test to show us where we are in the language after completing duolingo. (A1-C2)
This is not really feasible because those placement tests require reading and listening comprehension, writing and speaking ability. DuoLingo can only barely comment on the ability to write (eg., it's entirely possible to use the site without ever speaking). Listening exercises are not a meaningful indication of listening comprehension because they can be played at slow speed. It would maybe be more interesting to see the skill tree colour coded in some way to display progression of grammatical constructs that move from A1 to C2.