Language assessment is an activity guided by prevailing language ideologies as well as more general ideas that permeate the entire society. In this chapter, we will examine the ideologies of language proficiency descriptors and assessment, based on the theoretical perspectives of critical language testing (e.g. Lynch 2001; Shohamy 2001). More specifically, we will present some of the key concepts of the Common European Framework of Reference for Languages (CEFR, Council of Europe 2001, 2020a) and assessment based on the framework, especially on test assessment. With the help of concrete examples, we will also show that a deep understanding of the effects of language assessment and the development of assessment require recognition of both its ideology, its origin, and the mechanisms of its effects.