Just visited 9types.com & took their tests (they have 2). The first one returned 5, 7 and 9 with equal high scores. The second one returned 5 as highest, then 4, with 7 and 9 as the only other positive scores.
I've taken tests on other sites, and almost always come up with 7, 8 or 9 on them, with some 5s mixed in. But what's intriguing about the 9types site is that they have positive/negative cycle diagrams with short descriptions, and reading through the 9 diagrams, it really sounds like there's no way I could be 4, 6 or 8. Or a 1, 2, or 3, for that matter. That leaves 5, 7 and 9, and neither 5 nor 9 really sound like what motivates me, either through desire (9) or fear (5).
And yet, the briefness of the descriptions is limiting, because other, more substantial, descriptions reveal 7s to be far more gregarious and fantasizing than I really am. So, the tests aren't reliable, and the descriptions don't match. And neither the 6 nor 8 make sense as wings.
What is it again about the enneagram that so many people find useful?