Issue: when assert_redirected_to fails due to the response redirect not
matching the expected redirect the user-supplied message (second parameter)
is not shown. This message is only shown if the response is not a redirect.
assert_redirected_to login_path, "Expected redirect to login page"
... there is redirection not to login_path then we don't see "Expected redirect to login page." but only default "Expected response to be a redirect to /login but was a redirect to /other." message.
The issue was first mentioned in 2011 but was not fixed in 3.* branch. I faced with it several days ago.
In 4.* action_dispatch tests helpers were refactored so 4.* has no such bug.