I am not a fan of all these tests, but I think it may help to keep bigger percentage of newcomers stay on. Unfortunately, people get used to the scheme ‘learning = passing tests’. When I was a pupil, my parents always said: ‘It does not matter what marks you receive. Our final goal is knowledge.’ But for the majority of people learning goal is passing tests. They do not feel that they have learned anything until they pass some test. Some of them are even addicted to tests, I think.
And when people, assuming that there is no language learning without tests, come to LigQ and see
- Read & Listen
- LingQ New Words
- Submit Writing
- Speak to a Tutor
they don’t think that this site is serious and using this site can help them to learn language. So, they even don’t try to understand the system and go out.
Perhaps it would be nice to have several tests:
i. vocabulary tests
- fill-in-the-blank test
- listening comprehension (mmm… a student listen to lingqed word and have to choose right hint)
ii. grammar tests, like Helen has suggested above.
iii. content understanding (who is taller? Who is younger? for the second (?) episode of ‘Who is she?’ for example)
The last two tests can’t be composed automatically, that’s why they need to be composed manually. And it will be up to a provider/editors to create these tests. But I think that having such tests for a beginner content (especially for lessons from the English section of our library) will help to increase percentage of newcomers who give LingQ a try. They will see the sequence of tasks they get used to
- Read & Listen
- LingQ New Words
(Perhaps, it would be wise to add ‘Flashcard your lingqs’ task, to be sure that newcomers learn about this possibility from the first glance on any lesson)
- Test yourself
- Submit Writing (quick suggestion: it would be nice if providers and editors could define several default topics for a lesson. So, submitting writing for the lesson, a student can choose one of suggested topics or any other topic)
- Speak to a Tutor
Also average test score can be added to lingq statistics. Average test score for 1 day, 1 week, 1 month.
Oh! And graphics of your activity! For a last 6 months, for example. You can see the dynamics of your created and learned lingqs, read words, test scores, so on monthly, weekly, daily.
It seems I should stop now
I have too much suggestions. I understand that some of these suggestions do not correspond with LingQ method, but people get used to this way of learning languages. We can’t break all this paradigm in first 5 seconds. Newcomers look at LingQ lesson first 5 seconds, do not understand the paradigm LingQ is based on, close the tab and never return. But if we pretend to be ‘a serious language learning site’, newcomers perhaps will stay for some longer period. Later, they will understand and adopt this method of language learning and will become addicted with LingQ 
So, my opinion is: LingQ need to pretend to be ‘a serious language learning site’. (My coworkers call LingQ “шарашкина контора” — English-Russian Multitran dictionary )