I am a college Korean teacher, but I fail the 'test out' here...
My student ask me if it is good to learn Korean from 'duolingo'. So I tried one session, found out it was fine. Then I wanted to 'test out of 5 skills'. But failed three or four times. My Korean is definitely not perfect. But I am pretty sure that I am above the level of the test skills. However, I failed for the test and have a feeling that the test is 'awkward'. Not blaming anything, I just wants to provide some feedbacks to the builder here.
The translation of several words are not appropriate. For example, ''과자" is a general name of pastry, but it is 'cracker' in the test.
The boundary between 'singular' and 'plural' is not clear. Actually, Korean language itself does not have a clear line between singular words and plural words. The particle '들' is used when emphasising on plural, but not compulsory. So some of the test question strictly grades on the singular/plural form is not necessary.
Some of the sample sentences are strange to me because those sentences would never be used in daily life.
It is nice to find a free online Korean learning course. But it certainly need some revisions.
I just did the test and I already have basic Korean knowledge. I only got asked 3 questions that were weird. (The Korean word for stomach anyone? Supposed to be 위, but not something you'd ask in a basic knowledge quiz, right?) And then it decided I don't know anything.