Cancer gene test only paid for AFTER cancer is diagnosed for high-risk patient?

My wife's 33-year old sister has breast cancer. Two of my wife's aunts had breast cancer. I phoned Discovery to find out if they will pay for gene testing for the specific variant that runs in the family (my wife is classified as high risk). First I was told no, only when she has been diagnosed with cancer (as far as I'm aware, calls are recorded, they should then have this). So I asked if I understood correctly - they will not pay beforehand to assess my wife's risk, they will only pay to find out whether she has the cancer gene, once she has cancer? I was told this is correct. I told the agent I cannot believe this and asked to speak to a supervisor. She very rudely then transferred me to a supervisor (Shivanee - not sure about the spelling) who apologised for the agent's potentially life-threatening mistake. Shivanee told me 1 of the codes (tests) would indeed be covered. She would get back to me but had an emergency at home and was on leave. In the meantime I spoke to about 5-6 other agents, each time getting a different answer. Half said it would be covered, half said it won't. My wife did the test which we paid for ourselves and Discovery asked me to send the invoice, which I did. It was declined. Now I am just wondering whether I had once again managed to unluckily reach an agent that assessed the claim who is part of the 50% that believe it won't be covered, or whether it is indeed not covered? Every time I phone I get a different answer - who do I believe? And trying to speak to the same agent is impossible, seeing as when I request this I am told they all work in different call centers and don't know each other. And they don't have direct numbers.

So my question is the following: Will Discovery only pay for the gene test for cancer after my wife has developed cancer??? I am no medical or mathematical expert but believe prevention/monitoring would be considerably cheaper than treating??