Tidying code without breaking it

Computing · Software Engineering · ages 19-21

Name ______________________ Date ____________

What do you run between steps?
- The tests
- A farewell party
- The installer
What stays the same during refactoring?
- Observable behavior
- File names
- Line counts
Swapping a whole block at once counts as refactoring.
Circle one: True False
How do you rename and move a class safely?
- Move first, rename never
- Rename everything at once silently
- Rename first, move next, running throughout
How do you split the forty-line billing function?
- Rewrite it from memory
- Pull one named helper at a time and test each
- Delete two jobs to shorten it
A step turns red. What now?
- Ship it anyway
- Undo that one tiny step
- Rewrite the tests to fit
You knew behavior held since tests stayed green at each step.
Circle one: True False
A teammate bundles a bug fix into a tidy-up and calls it refactoring. What is the flaw?
- Tidy code needs no tests
- Fixes should never ship
- Behavior changed, so tests cannot vouch for sameness

Answer key

For grown-ups. Fold this page away before handing over the rest.

The tests · Green tests prove behavior held.
Observable behavior · Structure moves; behavior holds still.
False · That is a rewrite, not small steps.
Rename first, move next, running throughout · Separate steps keep each one undoable.
Pull one named helper at a time and test each · One pull plus one test run keeps it safe.
Undo that one tiny step · Tiny steps make undo cheap.
True · Green between steps is the evidence.
Behavior changed, so tests cannot vouch for sameness · Mixed behavior breaks the sameness proof.