The Art of Debugging

Remy Sharp presents debugging as a skill built through repeated exposure to bugs rather than through a single trick. He says the useful sequence is to replicate the problem, isolate the cause, and then eliminate it, often by reducing the problem to a smaller case and, when possible, turning it into a failing test.

Reading notes

#

• The article accompanies his 2015 Art of Debugging talk from Fronteers in Amsterdam.
• He says there is no silver bullet for debugging and that experience matters more than rules.
• He describes learning from bugs over time, including work on bugs for new employees at a company where this became the fastest way to gain practical experience.
• He notes that framework-heavy apps can require different tools, especially sourcemaps and framework-specific devtools.
• He says he rarely cross-browser tests because much of his work is plain JavaScript that should behave the same everywhere.
• He breaks debugging into three steps: replicate, isolate, and eliminate.
• Replication starts with confirming the bug, then gathering details about the user’s environment and the steps that led to the problem.
• Incognito mode and multiple browser profiles help rule out extensions, cookies, storage, and security settings.
• Isolation means stripping away anything unnecessary, such as disabling extensions one by one or pulling code into a smaller test case.
• Elimination often means writing a failing test and fixing the bug against that test.
• When a bug cannot be replicated, he treats it as a possible Heisenbug and considers whether the test environment or the debugger itself is affecting the result.
• He divides debugging approaches into inside out, where the source is known, and outside in, where the visual problem is known but the source is not.
• His preferred tools include Workspaces and real-time updates, console shortcuts, timeline screenshots, network inspection and replay, DOM breakpoints, throttling, and memory profiling.
• For memory leaks, he suggests comparing heap dumps and looking for items that remain after garbage collection.
• He ends by saying debugging has no single solution and that stepping away from the computer can also help solve problems.