MEPX
Chapter 6 of 10All chapters
  1. 1Why test
  2. 2Kinds of test
  3. 3What a good test looks like
  4. 4Fakes, stubs and mocks
  5. 5Coverage and flakiness
  6. 6Reproducing a bug
  7. 7Narrowing it down
  8. 8Reading the evidence
  9. 9Debuggers and tools
  10. 10The hard ones

Chapter 6 of 10

Reproducing a bug

The step people skip.

Make it happen on demand

Find the smallest reliable way to trigger the problem. Until you can cause it at will, you cannot tell whether a change fixed it or merely disturbed it.

  • Write down the exact input, environment and steps.
  • Turn the reproduction into a failing test before touching the code.

Reports are clues, not facts

A user describes what they noticed, not what happened. Ask what they expected, what they saw and when it started, then confirm it yourself.