In language testing, what are the differences between proficiency test and performance test? and what does each of them measure?

As we all know that Performance is measurable and is always measured against a set of standards and performance is graded differently under different environment and situations. For eg. in a maths test having full marks as 100 , it is understood that higher the candidate scores the better is his performance but if we are to consider the quality of the question paper to have been extremely difficult, even a 50% score would be considered a good performance. If we look at it from a different angle then a class 8 standard maths paper where a class 10 student scores 80% as against an average score of 70% by the rest of the class it will considered to be a poor performance even though he has scored the highest marks.

Proficiency on the other hand is the ability of one person to make the other understand as best as possible what he is trying to state or explain. 

Therefore in case of a language test it is Proficiency that is more important than Performance because a person with ability to learn by heart the grammar or the nuances of the language may perform well in a classroom environment but may not be able to communicate well enough to make the other person understand what he is trying to say.

So we can state that Performance measures knowledge but Proficiency measures the actual ability on a real time basis.  

Simply stated, Proficiency is the ability to use language in a real-world situation, Performance is the ability to use language in a limited and controlled situation such as a classroom or controlled situation-based exchange, and Achievement is the ability to repeat language elements that have been taught and mastered at some level. Each has a role in language learning, but only proficiency is what people use to communicate in the real world. 

I think performance test measures how far you are good at your job. But the proficiency test measures

how far your are experienced and distinguished at your job

In my opinion proficiency test checks, learners ability to use language in real situations. While as performance tasks are targeted to evaluate the knowledge in a limited environment such as a classroom or a curriculum benchmark. 

When one is proficient in a language he performs better. Proficiency tests compare a person's ability against a set of language descriptors. performance test shows how a person really able to deliver the language proficiently.  

To my knowledge, not as much of a difference. Both actually check one's level of mastering a language, as well as the level of knowledge already perceived. Both tests generaly check up what a student can do in certain tasks