editione1.0.1
Updated August 7, 2023Occasionally, you’ll come across code that you won’t understand no matter how many log statements you add. Wrapping your head around confusing code is frustrating, especially if you’re trying to figure out how some piece of data is being manipulated. While you may be able to figure it out with enough log statements, it’s messy to add them all over your codebase just to piece together what’s going on. Sometimes a debugger is the better tool for the job.
When you distill a program down to the simplest form, it’s really just taking some inputs, manipulating the data structures, and producing output somewhere. To really get a grasp on how everything works, you need to understand how the data changes as it moves through the system. While it’s helpful to read through code and build a mental model of what the data structure looks like, it’s sometimes easier to visualize the program with a debugger and observe how the data changes as it moves through the system.
If you have a debugger configured, you’ll be able to see what the data looks like at each breakpoint you set. As you step through the debugger, focus on the data and how it changes as you step in and out of functions.
An underrated technique for studying an unfamiliar codebase is to read through the automated tests. While it’s not the most glamorous part of the codebase, there’s an enormous amount of institutional knowledge stored in the test files. Automated tests are where past and present developers have codified the specifications the application is expected to operate within.
Most young developers don’t realize that a mature test suite will show you exactly how a program should perform, because each test that’s added to the suite should be designed to validate a specific part of the program for a specific scenario. As you read through the test cases, you’ll see what edge cases the tests handle and what the expected outcomes should be.
Additionally, the assertions in automated tests will show you what the expected output should be when you call a function. Assuming the tests are passing, this gives you a clear picture of how the system works and what application states you should expect.