Code Debugging while exploratory testing

Yesterday, I was reading a book “How we test software at Microsoft” by Alan page and his colleagues. I liked his approach of debugging the code before designing test cases or doing exploratory testing. I am quoting his words below:

“Frequently, when I am testing a component or feature for the first time and I have source code available, I use the debugger to test. Before I even write test cases, I write a few basic tests. These might be automated tests, or they might be just a few ideas that I have scribbled onto a pad. I set a breakpoint somewhere in the component initialization, and then use the debugger to understand how every code path is reached and executed. I note where boundary conditions need testing and where external data is used. I typically spend hours (and sometimes days) poking and prodding (and learning and executing) until I feel I have a good understanding of the component. At that point, I usually have a good idea of how to create an efficient and effective suite of tests for the component that can be used for the lifetime of the product.”