It can be compared with an achievement test, which evaluates a learner's understanding of specific material, a diagnostic test, which identify areas to work on, and a prognostic test, which tries to predict a learner's ability to complete a course or take an exam. Proficiency tests are uncommon within the classroom but very frequent as the end aim (and motivation) of language learning.
Example
IELTS and TOEFL are examples of proficiency tests.
In the classroom
Proficiency tests often have a significant backwash effect on the classroom, as learners' focus narrows to preparing the test items. One way to make practice for exams more meaningful is by asking learners to prepare their own practice questions for the group.
See also:
https://www.teachingenglish.org.uk/article/achievement-test
https://www.teachingenglish.org.uk/article/criterion-referenced-test
https://www.teachingenglish.org.uk/article/diagnostic-test
https://www.teachingenglish.org.uk/article/norm-referenced-test
https://www.teachingenglish.org.uk/article/objective-test
https://www.teachingenglish.org.uk/article/subjective-test
Further links:
https://www.teachingenglish.org.uk/article/assessment
https://www.teachingenglish.org.uk/article/testing-assessment
https://www.teachingenglish.org.uk/article/skills-techniques-link-speaking-writing-ielts
https://www.teachingenglish.org.uk/article/teenagers-exams-0
https://www.teachingenglish.org.uk/article/test-question-types
https://www.teachingenglish.org.uk/article/issues-language-testing
My sister is sitting for the IELTS exam.
But because of the Covid, I provided her some online courses. One of them was by the British council.
She wrote a review about the courses she took, in case you want to see them.
I'm very excited about her results!