Students acquire best when they do not feel tested (Krashen, 85). While summative tests may be needed occasionally, most assessments should be natural, authentic observations of how much students enjoy and comprehend input. It is sometimes difficult to communicate and document alternative assessments.
Here is a simple primer with 15 commonly asked questions and answers teachers may face about authentic assessment for second language learners.
Krashen, S. D. (2011). Free Voluntary Reading. Libraries Unlimited.