If this beta feature is enabled on your account, then you can create written response questions (in addition to multiple choice questions). When creating the test question, simply select the Answer Type that you’d like.
If you select Written Response, then you can set a minimum word count for the responses. If set, users must hit the minimum word count in their responses to pass the question. You can also leave the field blank to not require a minimum word count for responses, and then any user who submits an answer will get the question correct.
*Quick Tip: Since written responses may not always be graded correctly, it's a good idea to let your team know you'll review written response tests with them individually.