测试代码的理想时间表是什么？

I'm currently working on a critical monthly Accounts payable report. This report i just wrote will be the basis for my client in which how much is he going to pay to his vendors. So far i have spent about 5 hrs building automated tests and found zero errors so far. Do you think i am already spending too much time testing? What should be the ideal time-frame for testing?I'm currently working on a critical monthly Acc