never say always
In most cases, technical skill is enough, because most of the people who practice aikido are decent folk. In some very rare cases, a student may have a very serious attitude problem that may need to be overcome first, before a test and a promotion can be given. (In 25 years of aikido training, I have yet to see such a situation arise.)
The bigger problem in aikido, as I see it, is that some students are too passive and they are unwilling to test at all. Gutless martial-arts students should be a contradiction in terms, but aikido, for some reason, seems to attract them.