Agreed. In general, if you're having trouble tracing through a particular function with a narrow band of input, then the debugger can be useful. If you're try

Agreed. In general, if you're having trouble tracing through a particular function with a narrow band of input, then the debugger can be useful. If you're trying to figure out a larger system and/or how a system works across a large set of inputs, then stepping through with a debugger is useless. Put another way, the debugger is to programming what the microscope is to medicine: incredibly useful for some things, but not a very good general diagnostic tool. Metrics data and checking assumptions (via unittest and/or asserting expectations based on reading the code) are much better for getting an over-all idea of what's going on. Once you've localized a problem, then the debugger can help you get a precise idea of the issue, or can help you test a hypothesis (to use the medical example, you can use the microscope to test a theory that there's a bacterial infection).