This study was undertaken to address an issue of student retention and learning in undergraduate computer science (CS) courses. To improve students' CS learning experience, the goal of this case study was to support five CS faculty's integration of active learning into their teaching, using the Understanding by Design framework. We explored the CS faculty's considerations and experiences with active learning integration. The data included video conferencing recordings, syllabi data analysis, teacher interviews, and a focus group. The results showed that CS faculty considered three aspects in their active learning integration: (a) course structure and delivery format, (b) instructional approaches, and (c) authentic learning experiences for students. The CS faculty's primary challenge was ways to assess individual students' knowledge gained in team-based activities. We found a gradual adaptation of active learning in CS faculty's teaching practices and recognized that their development and change in pedagogies need time and personalized support.