Okay. I missed that on the first reading.
Reading over the Ennegram thing reminds me of looking at a horoscope. People who are easily influenced by suggestion see themselves in it, and interpret life through it.
Unfortunately, there seems to be a large pool of weak-minded people who are desperately looking to any and every source they can find to understand their self and life.
The gospel of salvation notwithstanding, isn't that what the Bible provides for us?
That said, I do think the MBTI, CPI, Strong Inventory and some others provide "snapshots" or views of personality that are helpful in general terms.
The problems arise when people move from a general appreciation type as a tool, to stereotyping and pigeonholing others into boxes or categories like cats or sweaters. We've all done it, and we've all been subjected to it.
Back to the basic question, there are tests that are well researched and that hold validity. The area of psychology you want to look into is called psychometry, or if you prefer, psychometrics.