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backend apis

Put a messy function under test

Take untested, tangled code and get it covered without changing what it does.

beginnerPython~10h

Why it matters

Greenfield testing is easy. Every real job involves code somebody else wrote badly, and being able to make it safe to change is immediately useful on day one.

What you build

  • Characterisation tests that capture current behaviour
  • Dependencies isolated so tests run fast
  • A refactor proven safe by the tests
  • Coverage that means something

If you want more

  • Add property-based tests
  • Wire coverage into CI

Build it 5 steps

  • You are recording behaviour, not judging it. That comes next.

  • Refactor now that the tests hold you

Material for the whole build

Shows you can make existing code safe to change, which is most of what maintenance work is.

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