The goal in personalized assessment is to best fit the needs of each individual test taker, given the assessment purposes. Design-In-Real-Time (DIRTy) assessment reflects the progressive evolution in testing from a single test, to an adaptive test, to an adaptive assessment "system." In this paper, we lay the foundation for DIRTy assessment and illustrate how it meets the complex needs of each individual learner. The assessment framework incorporates culturally responsive assessment principles, thus making it innovative with respect to both technology and equity. Key aspects are (a) assessment building blocks called "assessment task modules" (ATMs) linked to multiple content standards and skill domains, (b) gathering information on test takers' characteristics and preferences and using this information to improve their testing experience, and (c) selecting, modifying, and compiling ATMs to create a personalized test that best meets the needs of the testing purpose and individual test taker. [This paper will be published in "Educational Measurement: Issues and Practice."]