I actually declared a CS certificate last year as an undergrad. The certificate requirements could also fulfill the credits needed for my engineering and science electives, and I enjoyed learning Python and MATLAB, so it seemed like a great choice for me. However, I tried to take CS 300 (Java), and it was too difficult, so I ended up having to drop it. Since CS 300 is required for the certificate, I will no longer be pursuing it. If you have some experience with Java or are able to learn it before taking CS 300, I would definitely recommend the certificate! However, I am not sure if can be completed during a graduate program.