RLM TDD Discipline

Overview

Test-Driven Development is mandatory for all RLM implementation work. This skill ensures test-first discipline is followed rigorously.

Core Principle: If you didn't watch the test fail, you don't know if it tests the right thing.

The Iron Law for RLM:

NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST

Trigger examples

• Implement Phase 3 for run '2026-02-24-add-oauth'
• Add a failing regression test first, then fix the bug
• I already wrote the code; now add tests (should trigger TDD reset guidance)
• Follow RED-GREEN-REFACTOR for this change

When to Use

Always in Phase 3 (Implementation):

• New features
• Bug fixes
• Refactoring
• Behavior changes

No Exceptions:

• Not for "simple" changes
• Not when "under pressure"
• Not because "tests after achieve same goals"

RED-GREEN-REFACTOR Cycle

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"];
    record [label="Record in\nPhase 3 artifact", shape=box];

    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 -> record;
}

RED - Write Failing Test

Write one minimal test showing what should happen.

Requirements:

• One behavior per test
• Clear, descriptive name
• Test real code (no mocks unless unavoidable)
• Clear assertion showing expected outcome

<Good>

test('rejects empty email with clear error message', async () => {
  const result = await submitForm({ email: '' });
  expect(result.error).toBe('Email is required');
});

</Good>

<Bad>

test('email validation works', async () => {
  const mock = jest.fn().mockResolvedValue({ valid: true });
  const result = await validateEmail(mock);
  expect(mock).toHaveBeenCalled();
});

</Bad>

Verify RED - Watch It Fail

MANDATORY. Never skip.

npm test path/to/test.test.ts

Confirm:

• Test fails (not errors)
• Failure message is expected
• Fails because feature missing (not typos)

Record in Phase 3 artifact:

### TDD Cycle for R3 (Email Validation)

**RED Phase:**
- Test: `rejects empty email with clear error message`
- Command: `npm test src/forms/email.test.ts`
- Expected failure: "Email is required" not found
- Actual failure: [paste output]
- RED verified: ✅

GREEN - Minimal Code

Write simplest code to pass the test.

Rules:

• Just enough to pass
• No additional features
• No "while I'm here" improvements
• No refactoring yet

<Good>

function submitForm(data: FormData) {
  if (!data.email?.trim()) {
    return { error: 'Email is required' };
  }
  // ... rest of form handling
}

</Good>

<Bad>

function submitForm(
  data: FormData,
  options?: {
    strictMode?: boolean;
    customValidators?: Validator[];
    onValidationError?: (err: Error) => void;
  }
) {
  // YAGNI - over-engineered
}

</Bad>

Record in Phase 3 artifact:

**GREEN Phase:**
- Implementation: Added null check for email field
- Command: `npm test src/forms/email.test.ts`
- Result: PASS
- GREEN verified: ✅

REFACTOR - Clean Up

After green only:

• Remove duplication
• Improve names
• Extract helpers
• Keep tests green

Never add behavior during refactor.

Record in Phase 3 artifact:

**REFACTOR Phase:**
- Extracted `validateRequired(field, name)` helper
- Renamed `submitForm` to `processFormSubmission` for clarity
- All tests still passing: ✅

Common Process Shortcuts (STOP)

Red Flags - STOP and Start Over

If you encounter any of these, DELETE CODE and restart with TDD:

• ❌ Code written before test
• ❌ Test passes immediately (not testing what you think)
• ❌ "I'll add tests later"
• ❌ "This is too simple to test"
• ❌ "I know what I'm doing, I don't need the ritual"
• ❌ Can't explain why test failed (or didn't fail)
• ❌ Test testing mock behavior, not real behavior
• ❌ Multiple behaviors in one test ("and" in test name)

Integration with RLM Phase 3

Phase 3 Artifact TDD Section

Every Phase 3 artifact must include:

## TDD Compliance Log

### Requirement R1 (Feature X)

**Test:** `test/features/x.test.ts` - "should do Y when Z"
- RED: [timestamp] - Failed as expected: [output]
- GREEN: [timestamp] - Minimal implementation: [description]
- REFACTOR: [timestamp] - Cleanups: [description]
- Final state: ✅ All tests passing

### Requirement R2 (Bug Fix)

**Regression Test:** `test/bugs/issue-123.test.ts` - "reproduces crash on empty input"
- RED: [timestamp] - Confirmed bug: [output]
- GREEN: [timestamp] - Fix applied: [description]
- REFACTOR: [timestamp] - N/A (minimal fix)
- Final state: ✅ Test passes, bug fixed

Phase 3 Coverage Gate Addition

## Coverage Gate

- [ ] Every new function has a corresponding test
- [ ] Every bug fix has a regression test that fails before fix
- [ ] All RED phases documented with failure output
- [ ] All GREEN phases documented with minimal implementation
- [ ] All tests passing (no skipped tests)
- [ ] No production code written before failing test

TDD Compliance: PASS / FAIL

Phase 3 Approval Gate Addition

## Approval Gate

- [ ] TDD Compliance: PASS
- [ ] Implementation matches Phase 3 plan
- [ ] No code without preceding failing test
- [ ] All tests documented in TDD Compliance Log

Approval: PASS / FAIL

Bug Fix TDD Procedure

1. Add Regression Test First

- Write test that reproduces the bug - Run test, confirm it fails with expected error - Document failure in Phase 3 artifact

1. Implement Minimal Fix

- Fix only what's needed to make test pass - Run test, confirm it passes - Document fix in Phase 3 artifact

1. Verify No Regressions

- Run full test suite - Confirm nothing else broke - Document in Phase 3 artifact

1. Lock Phase 3

- TDD Compliance: PASS - Approval: PASS - Status: LOCKED

Example: Complete Phase 3 TDD Section

## TDD Compliance Log

### R1: Add email validation

**Test:** `test/forms/validation.test.ts`

RED Phase (2026-02-21T10:15:00Z):

$ npm test test/forms/validation.test.ts FAIL: Expected 'Email is required', got undefined

RED verified: ✅

GREEN Phase (2026-02-21T10:18:00Z):
- Added null check in `submitForm()` function
- Test passes
GREEN verified: ✅

REFACTOR Phase (2026-02-21T10:22:00Z):
- Extracted `validateRequired()` helper
- All tests still passing
REFACTOR complete: ✅

### R2: Fix crash on empty array

**Regression Test:** `test/utils/array.test.ts`

RED Phase (2026-02-21T10:25:00Z):

$ npm test test/utils/array.test.ts FAIL: TypeError: Cannot read property 'map' of undefined

RED verified: Bug reproduced ✅

GREEN Phase (2026-02-21T10:27:00Z):
- Added guard clause in `processItems()`
- Test passes
GREEN verified: ✅

REFACTOR: N/A (minimal 2-line fix)

## Verification

Full suite run: `npm test`
Result: 47 passing, 0 failing

References

• REQUIRED: Follow this skill for all Phase 3 implementation work