The primary purpose of language testing is to measure an individual's language proficiency, which refers to their ability to use a language effectively and appropriately in different contexts.

Achievement tests are not typically used in language testing, as they are designed to measure what a student has learned in a specific course or program, rather than their overall language proficiency.

Proficiency tests are designed to measure an individual's overall language ability, while placement tests are designed to measure specific language skills, such as reading, writing, listening, and speaking, in order to determine the appropriate level of instruction for the individual.

All of the above are ethical considerations in language testing. Tests should be fair and unbiased, meaning that they should not discriminate against any particular group of people. Tests should be valid and reliable, meaning that they should accurately measure what they are intended to measure. Tests should be administered in a secure and confidential manner, meaning that the results should not be disclosed to unauthorized individuals.

All of the above are roles of language testing in language policy. Language tests can be used to determine which languages are taught in schools, to assess the effectiveness of language programs, and to identify students who need additional language support.