Bug Fixer is a web-based application that complements lectures with hands-on exercises that encourage students to think about the logic in programs. Bug Fixer presents students with code that has several bugs that they must fix. The process of fixing the bugs forces students to conceptually think about the code and reinforces their understanding of the logic behind algorithms. In this work, we conducted a study using Bug Fixer with undergraduate students in the CSCE1040 course at University of North Texas to evaluate whether the system increases their conceptual understanding of the algorithms and improves their Software Testing skills. Students participated in weekly activities to fix bugs in code. Most students enjoyed Bug Fixer and recommend the system for future use. Students typically reported a better understanding of the algorithms used in class. We observed a slight increase of passing grades for students who participated in our study compared to students in other sections of the course with the same instructor who did not participate in our study. The students who did not report a positive experience provide comments for future improvements that we plan to address in future work.