A lack of resources exists outside of the classroom to aid electrical and computer engineering students in the understanding of the basic fundamentals of digital design topics. The Combinational Logic Design Tool (CLDT) provides students with the ability to gauge their own progress in their classes while allowing them to be self as well as lifelong learners. CLDT is designed to work with the students' base knowledge and through practice improve this knowledge and expand it. It is also designed to help students develop their self-monitoring skills. No purely assessment tools exist in the area of digital logic design and hence CLDT is expected to fill a large void in terms of online assessment/practice tools. This paper describes research that produces a complete interactive online assessment tool to assess students' knowledge of the process of designing and implementing a combinational logic circuit.