Computational thinking (CT), a transversal intellectual foundation integral to computer science, is making its way into compulsory comprehensive education worldwide. Students are expected to attain skills and knowledge in such interdisciplinary CT principles as Algorithmic thinking, Data representation, and Debugging. Problem-solving by designing and manipulating interactive media with Scratch, a graphical programming tool, is popular especially at the primary school level. However, there has been confusion regarding how introductory CT can be operationalized for educational practice. Teachers and students need research-based knowledge for setting appropriate learning goals in addition to instruments for formative assessment that potentially improve the quality of learning. This study contributes to these issues by developing the assessment for learning of CT via Scratch in primary school settings. A review on prior studies involving the assessment of CT-related computational ideas in Scratch has led to the conceptualization of a revised assessment framework. Next steps in the study are analyzing fourth grade students' (N=58) Scratch projects and exploring complementary methods for analyzing CT in video recordings of the students' programming processes.