> Could please use assert_raise_message to check that the exception message
is informative as well?

Personally, I really don't like hardcoding error messages in tests. Those
tests are a pain to create and a pain to maintain (in case you need to fix
typos etc). And if you go through the pain of copy/pasting messages from
one place to another, you might as well make your messages informative from
the beginning. This was my little evening rant :)