This chapter explores how principles of language assessment can and should be applied to formal test but with the ultimate recognition that these principles also apply to assessment of all kinds. In this chapter,these principles are defined and discussed with reference to classroom-based assessment in particular. They are then rephrased in the form of a set of "trips" for testing that can be applied to a number of different kinds of classroom assessments. Chapter 3 then focuses on using these principles, step-by-step, in the actual design of classroom-based tests.