A program that Thomas has written is complete. It has been tested thoroughly, and some outputs were not as expected. Thomas is now going through the code carefully attempting to establish the cause of these errors and change the code to remove them. What is this procedure called? Thomas 编写的程序已完成。它已经过全面测试，但有些输出不符合预期。Thomas 现在正在仔细检查代码，试图找出这些错误的原因并修改代码以消除它们。这个过程叫什么？