Write a test plan for a change to code that has no tests yet
"Just add tests" isn't a plan when the code being changed has none to build on.
- Use it for
- Anyone changing legacy or untested code who needs a real test plan, not just a vague intention to test it.
Changing code with no existing tests often gets a vague intention — "I should add some tests" — instead of an actual plan, which means the tests that get written are whatever's easiest to write, not what actually protects against regressions in the specific change being made. This prompt builds a real, prioritized test plan first: what behavior the change must preserve, what's actually risky, and what order to write tests in before touching the code.
When not to use this
If the codebase already has solid test coverage around the area you're changing, this full planning exercise is unnecessary — just extend the existing tests. This is for genuinely untested code.
Did this work?
You have a specific, prioritized list of tests to write before touching the code, not a vague intention to "add test coverage."
Tested on claude-opus-5. Evidence status is draft; it moves to battle-tested only on recorded runs, never by hand.