measure dev/urandom efficiency

I have to measure efficiency of /dev/urandom as an assignment. I've got the following task: Check, how many bytes of data you can get from /dev/urandom in 1 minute. Don't write taken data on disk, as it could slow everything down.

I've tried

timeout 60s cat /dev/urandom | wc -c

But all I receive was just "Terminated" message.