RED-GREEN-REFACTOR cycle with testing anti-patterns reference
Catalog skill by obra: RED-GREEN-REFACTOR cycle with testing anti-patterns reference Install into Cursor, Claude, Codex, or VS Code from this page or review the source for Test-Driven Development.
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/plugin install superpowers@superpowers-marketplace
Install guides: Cursor skills, Claude Code skills, Codex skills, or VS Code Copilot skills.
Write the test first. Watch it fail. Write minimal code to pass.
Core principle: If you didn't watch the test fail, you don't know if it tests the right thing.
Violating the letter of the rules is violating the spirit of the rules.
Always:
Exceptions (ask your human partner):
Thinking "skip TDD just this once"? Stop. That's rationalization.
NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST
Write code before the test? Delete it. Start over.
No exceptions:
Implement fresh from tests. Period.
digraph tdd_cycle {
rankdir=LR;
red [label="RED\nWrite failing test", shape=box, style=filled, fillcolor="#ffcccc"];
verify_red [label="Verify fails\ncorrectly", shape=diamond];
green [label="GREEN\nMinimal code", shape=box, style=filled, fillcolor="#ccffcc"];
verify_green [label="Verify passes\nAll green", shape=diamond];
refactor [label="REFACTOR\nClean up", shape=box, style=filled, fillcolor="#ccccff"];
next [label="Next", shape=ellipse];
red -> verify_red;
verify_red -> green [label="yes"];
verify_red -> red [label="wrong\nfailure"];
green -> verify_green;
verify_green -> refactor [label="yes"];
verify_green -> green [label="no"];
refactor -> verify_green [label="stay\ngreen"];
verify_green -> next;
next -> red;
}
Write one minimal test showing what should happen.
const result = await retryOperation(operation);
expect(result).toBe('success'); expect(attempts).toBe(3); });
Clear name, tests real behavior, one thing
</Good>
<Bad>
```typescript
test('retry works', async () => {
const mock = jest.fn()
.mockRejectedValueOnce(new Error())
.mockRejectedValueOnce(new Error())
.mockResolvedValueOnce('success');
await retryOperation(mock);
expect(mock).toHaveBeenCalledTimes(3);
});
Vague name, tests mock not code
Requirements:
MANDATORY. Never skip.
npm test path/to/test.test.ts
Confirm:
Test passes? You're testing existing behavior. Fix test.
Test errors? Fix error, re-run until it fails correctly.
Write simplest code to pass the test.
Don't add features, refactor other code, or "improve" beyond the test.
MANDATORY.
npm test path/to/test.test.ts
Confirm:
Test fails? Fix code, not test.
Other tests fail? Fix now.
"Other tests" means the project's suite, not just your file. A
green run of the test you wrote is not a green suite. Before you call
the change done, run the project's test command (bare pytest,
npm test, cargo test — whatever the repo uses) even when your task
named only one test file. A scope statement in your task bounds the
deliverable, not your verification. Any failure that run shows —
including one you didn't cause — goes in your report by name; a red
test you watched scroll past and didn't mention is a report falsified
by omission.
After green only:
Keep tests green. Don't add behavior.
Next failing test for next feature.
| Quality | Good | Bad |
|---|---|---|
| Minimal | One thing. "and" in name? Split it. | test('validates email and domain and whitespace') |
| Clear | Name describes behavior | test('test1') |
| Shows intent | Demonstrates desired API | Obscures what code should do |
When writing or changing any test, read writing-good-tests.md for the rules that keep tests honest:
| Excuse | Reality |
|---|---|
| "Too simple to test" | Simple code breaks. Test takes 30 seconds. |
| "I'll test after" | Tests written after pass immediately — which proves nothing. They may test the wrong thing, test the implementation instead of the behavior, or miss the edge case you forgot. You never watched it fail, so you never proved it can catch the bug. Test-first forces that failure. |
| "Tests after achieve same goals (spirit not ritual)" | Tests-after answer "what does this do?"; tests-first answer "what should this do?" Tests written after are biased by the code you already wrote — you verify the cases you remembered, not the ones you'd have discovered. Coverage without proof the tests work. |
| "Already manually tested" | Manual testing is ad-hoc: no record of what you covered, no way to re-run it when the code changes, easy to forget cases under pressure. "Worked when I tried it" ≠ comprehensive. Automated tests run the same way every time. |
| "Deleting X hours is wasteful" | Sunk cost fallacy — that time is already spent either way. The real choice: rewrite with TDD (high confidence) vs. keep it and bolt tests on after (low confidence, likely bugs). Keeping code you can't trust is the waste. |
| "Keep as reference, write tests first" | You'll adapt it. That's testing after. Delete means delete. |
| "Need to explore first" | Fine. Throw away exploration, start with TDD. |
| "Test hard = design unclear" | Listen to test. Hard to test = hard to use. |
| "TDD will slow me down" | TDD IS the pragmatic path: catches bugs before commit, prevents regressions, lets you refactor without fear. "Pragmatic" shortcuts mean debugging in production — slower, not faster. |
| "Manual test faster" | Manual doesn't prove edge cases. You'll re-test every change. |
| "Existing code has no tests" | You're improving it. Add tests for existing code. |
All of these mean: Delete code. Start over with TDD.
Bug: Empty email accepted
RED
test('rejects empty email', async () => {
const result = await submitForm({ email: '' });
expect(result.error).toBe('Email required');
});
Verify RED
$ npm test
FAIL: expected 'Email required', got undefined
GREEN
function submitForm(data: FormData) {
if (!data.email?.trim()) {
return { error: 'Email required' };
}
// ...
}
Verify GREEN
$ npm test
PASS
REFACTOR Extract validation for multiple fields if needed.
Before marking work complete:
Can't check all boxes? You skipped TDD. Start over.
| Problem | Solution |
|---|---|
| Don't know how to test | Write wished-for API. Write assertion first. Ask your human partner. |
| Test too complicated | Design too complicated. Simplify interface. |
| Must mock everything | Code too coupled. Use dependency injection. |
| Test setup huge | Extract helpers. Still complex? Simplify design. |
Bug found? Write failing test reproducing it. Follow TDD cycle. Test proves fix and prevents regression.
Never fix bugs without a test.
Production code → test exists and failed first
Otherwise → not TDD
No exceptions without your human partner's permission.