TDD Red → Green → Refactor

We are implementing the following using strict TDD. Do not write any implementation code until I tell you to.

Feature: [DESCRIBE THE FEATURE]
Acceptance criteria: [WHAT DOES "DONE" LOOK LIKE , BE SPECIFIC]

Work through these steps in order. Complete each step fully before moving to the next. Mark each step with [RED], [GREEN], or [REFACTOR] so I can track where we are.

STEP 1 , [RED] Write failing tests

Write the tests that verify the acceptance criteria above.
Rules:
- Tests must assert the desired behavior, not the implementation
- Tests must fail right now (we have not written the code yet)
- Use real assertions , not expect(true).toBe(true)
- Cover: the happy path, at least one edge case, and at least one error state
- Do NOT use 0 or empty string as the only test data for math or logic tests
- Do NOT write tests that pass trivially

Commit message when done: "test: [feature name] , failing tests"
Tell me: "Tests are written and failing. Ready to implement."

STEP 2 , [GREEN] Write the minimum code to make tests pass

Write only the code needed to make every test pass. Nothing extra.
Rules:
- Do NOT add features not tested
- Do NOT optimize, generalize, or future-proof
- Ugly code that passes tests is correct at this step

Commit message when done: "feat: [feature name] , tests passing"
Tell me: "All tests passing. Ready to refactor."

STEP 3 , [REFACTOR] Clean up without breaking tests

Improve the code quality. Run tests after every change.
Rules:
- Tests must still pass after every refactor
- Remove duplication
- Improve naming
- Split large functions
- Do NOT add new functionality

If any test breaks during refactor: STOP, show me which test and why, fix it before continuing.

Commit message when done: "refactor: [feature name] , clean implementation"
Tell me: "Refactor complete. All tests still passing."