This study examined whether two integrated reading-to-write tasks could broaden the construct representation of the writing component of Duolingo English Test (DET). It also verified whether they could enhance DET's predictive power of English academic writing in universities. The tasks were (1) writing a summary based on two source texts and (2) writing a reading-to-write essay based on five texts. Both were given to a sample (N = 204) of undergraduates from Hong Kong. Each participant also submitted an academic assignment written for the assessment of a disciplinary course. Three professional raters double-marked all writing samples against detailed analytical rubrics. Raw scores were first processed using Multi-Faceted Rasch Measurement to estimate inter- and intra-rater consistency and generate adjusted (fair) measures. Based on these measures, descriptive analyses, sequential multiple regression, and Structural Equation Modeling were conducted (in that order). The analyses verified the writing tasks’ underlying component constructs and assessed their relative contributions to the overall integrated writing scores. Both tasks were found to contribute to DET's construct representation and add moderate predictive power to the domain performance. The findings, along with their practical implications, are discussed, especially regarding the complex relations between construct representation and predictive validity.