Test refunds on Authorize.net using a test account?

Question

I am developing a website that uses Authorize.net but I am currently using a test account. To test a refund, it requires a unique transaction ID, but since I am only using a test account, it does not return a unique transaction ID when you make a test transaction (always 2147483647). Is there another way for this to work? I need to see if my code will work with the API.