what is the primary purpose of language testing

[shining]

Since the last two decades, language testing has been the main focus of interest to many lanugage researchers and even teachers. Here, the question I want to ask is about the primary purpose of language testing. I think the exploration of question will help us better understand the language testing . I hope I can get proper responses to the question.
Thank you!

[rainbow]

In my opinion, the primary purpose of language is to measure the students' proficiency in the language ,to diagnosis the students' strengths and weaknesses, and to enhance teaching and learning.