How to make sure a partner in a business idea won´t turn against you?

There is a certain entrepreneur who wants to invest in my business idea. He has the money and I have the ideas. However, he is also smart enough to turn on me later when things start going well. I am sure this is a common fear between entrepreneurs who come together.

First, I would have to clarify that although I know this man little, we have developed a small friendship over a period of three months. He seems to be a person of good faith, and we have a lot in common. But I must admit that I don’t know him enough, and even the devil can smile.

How would I go about making sure this man won’t run off with my idea the moment I give him details?
How do I make sure this man won’t throw me off later down the road?
Are there contracts to sign of any kind?

Are there any tests I should do to test his loyalty?

All suggestions relevant to business start-up are welcome.