While Snapchat will not notify you of being blocked,
if you have the suspicion that someone blocked you,
there are a few ways to tell
that you have most likely been blocked.
If you've been sending snaps to each other,
check your chat tab.
If your previous or current snaps have disappeared,
you may have been blocked.
If you're friends on Snapchat, check your friends list.
If you no longer see them,
this could be an indication that they blocked you.
Try searching their username
using the spotlight at the upper left corner.
If it doesn't appear, they may have blocked you.
However, keep in mind
that the person you believe may have blocked you
could have deleted their account.
To confirm, ask a friend to search their username.
If it shows up on your friend's account but not your own,
you may have been blocked.