ABSTRACT
The title of this chapter suggests a description of a common practice of assessing language ability in second language acquisition (SLA) and applied linguistic research. However, the reader might be disappointed to learn that there is no common practice. The assessment of language ability is too complex to be captured in one common practice. Language ability per se is a complicated, multifaceted construct, consisting of many interdependent or independent subskills, and each subskill can be operationalised in many different ways. Moreover, language ability is assessed for many different purposes, and these purposes affect decisions about how language tests are designed.
