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Here's a preview from my zine, The Pocket Guide to Debugging! If you want to see more comics like this, sign up for my saturday comics newsletter or browse more comics!

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It’s much easier to debug when your program does the exact same thing every time you run it.

Illustration of a sad stick figure with curly hair.

person (thinking): “the bug only happens 10% of the time, it’s SO HARD to figure out if my change fixed it or not.”

There are a bunch of tools for controlling your program’s inputs to reduce randomness, for example:

  • many random number generators let you set the seed so you get the same results every time.
  • faketime fakes the current time.
  • libraries like ruby’s vcr can record http requests.
  • record/replay debuggers like rr record everything.