I recently started participating in code review site.
On my first question, the algorithm tag was inserted by an edit from a moderator, and soon yet another user suggested that I include a unit test.
Even though this might be a bit of a coincidence, I completely agree with the need of test cases when an algorithm is concerned.
I would like to suggest that we recommend a unit test be included with the algorithm tag, to prevent any code break.
I am suggesting an addition to code review help center or somewhere in UI.
Unless I have missed something, I think this might be a good addition.