There is an British proverb which says: "The beaten road is the safest" which is used to indicate the fact that testing somebody / something that has been once tested in the past is not required.
Example 1) Suppose you as the directing manager of a company are going to employ a marketing manager for your most important agency's marketing team in one of the country's biggest provinces. You have someone in your mind and bring it up to your deputy. He/she says: "I guess we have to test him o see if he has what it takes for this job or not! What do the Americans say here as a proverb to avoid saying: "I have tested him in the past and I'm sure he can manage to do his tasks properly?
Is it possible to say: "the beaten road is the safest"
Example 2) Suppose you have tested a camera which you have purchased recently. You are going to take a travel and take it with you for taking pictures in the trip. Your wife doesn't know that you have tested it yet. She tries to know if it works properly or not. You say I have tested it once and that's enough...(The beaten road is the safest)
I need to know if there is an American English equivalent for this saying or not.