Of paramount importance in the study of cognitive diagnostic assessment (CDA) is the absence of tests developed for small-scale diagnostic purposes. Currently, much of the research carried out has been mainly on large-scale tests, e.g., TOEFL, MELAB, IELTS, etc. Even so, formative language assessment with a focus on informing instruction and engaging in identification of student’s strengths and weaknesses to guide instruction has not been conducted in the Iranian English language learning context. In an attempt to respond to the call for developing diagnostic tests, this study explored developing a cognitive diagnostic reading comprehension test for CDA purposes. To achieve this, initially, a list of reading attributes was prepared based on the literature and then the attributes were used to construct 20 reading comprehension items. Then seven content raters were asked to identify the attributes of each item of the test. To obtain quantitative data for Q-matrix construction, the test battery was administered to 1986 students of a General English Language Course at the University of Tehran, Iran. In addition, 13 students were recruited to participate in think-aloud verbal protocols. On the basis of the overall agreement of the content raters’ judgements concerning the choices of attributes and results of think-aloud verbal protocol analysis, a Q-matrix that specified the relationships between test items and target attributes was developed. Finally, to examine the CDA of the test, the Fusion Model, a type of cognitive diagnostic model (CDM), was used for diagnosing the participants' strengths and weaknesses. Results suggest that nine major reading attributes are involved in these reading comprehension test items. The results obtained from such cognitive diagnostic analyses could be beneficial for both teachers and curriculum developers to prepare instructional materials that target specific weaknesses and inform them of the more problematic areas to focus on in class in order to plan for better instruction.
