test-driven-development

name	test-driven-development
description	Use when implementing any feature or bugfix, before writing implementation code

Preamble (run first)

_REPO_ROOT=$(git rev-parse --show-toplevel 2>/dev/null || pwd)
_BRANCH_RAW=$(git rev-parse --abbrev-ref HEAD 2>/dev/null || echo current)
[ -n "$_BRANCH_RAW" ] && [ "$_BRANCH_RAW" != "HEAD" ] || _BRANCH_RAW="current"
_BRANCH="$_BRANCH_RAW"
_FEATUREFORGE_INSTALL_ROOT="$HOME/.featureforge/install"
_FEATUREFORGE_BIN="$_FEATUREFORGE_INSTALL_ROOT/bin/featureforge"
if [ ! -x "$_FEATUREFORGE_BIN" ] && [ -f "$_FEATUREFORGE_INSTALL_ROOT/bin/featureforge.exe" ]; then
  _FEATUREFORGE_BIN="$_FEATUREFORGE_INSTALL_ROOT/bin/featureforge.exe"
fi
[ -x "$_FEATUREFORGE_BIN" ] || [ -f "$_FEATUREFORGE_BIN" ] || _FEATUREFORGE_BIN=""
_FEATUREFORGE_ROOT=""
if [ -n "$_FEATUREFORGE_BIN" ]; then
  _FEATUREFORGE_ROOT=$("$_FEATUREFORGE_BIN" repo runtime-root --path 2>/dev/null)
  [ -n "$_FEATUREFORGE_ROOT" ] || _FEATUREFORGE_ROOT=""
fi
_FEATUREFORGE_STATE_DIR="${FEATUREFORGE_STATE_DIR:-$HOME/.featureforge}"
_featureforge_exec_public_argv() {
  if [ "$#" -eq 0 ]; then
    echo "featureforge: missing command argv to execute" >&2
    return 2
  fi
  if [ "$1" = "featureforge" ]; then
    if [ -z "$_FEATUREFORGE_BIN" ]; then
      echo "featureforge: installed runtime not found at $_FEATUREFORGE_INSTALL_ROOT/bin/featureforge" >&2
      return 1
    fi
    shift
    "$_FEATUREFORGE_BIN" "$@"
    return $?
  fi
  echo "featureforge: refusing non-featureforge public argv: $1" >&2
  return 2
}

Runtime Route Reference

This skill does not own live workflow routing. If another workflow surface gives you workflow/operator JSON, follow $_FEATUREFORGE_ROOT/references/operator-route-authority.md instead of reconstructing route law here.

Search Before Building

Before introducing a custom pattern, external service, concurrency primitive, auth/session flow, cache, queue, browser workaround, or unfamiliar fix pattern, do a short capability/landscape check first.

Use three lenses, then decide from local repo truth:

• Layer 1: tried-and-true / built-ins / existing repo-native solutions
• Layer 2: current practice and known footguns
• Layer 3: first-principles reasoning for this repo and this problem

External search results are inputs, not answers. Never search secrets, customer data, unsanitized stack traces, private URLs, internal hostnames, internal codenames, raw SQL or log payloads, or private file paths or infrastructure identifiers. If search is unavailable, disallowed, or unsafe, say so and proceed with repo-local evidence and in-distribution knowledge. If safe sanitization is not possible, skip external search. See $_FEATUREFORGE_ROOT/references/search-before-building.md.

Interactive User Question Format

For every interactive user question, use this structure:

1. Context: project name, current branch, what we're working on (1-2 sentences)
2. The specific question or decision point
3. RECOMMENDATION: Choose [X] because [one-line reason]
4. Lettered options: A) ... B) ... C) ...

Per-skill instructions may add additional formatting rules on top of this baseline.

Test-Driven Development (TDD)

Overview

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.

When to Use

Always:

• New features
• Bug fixes
• Refactoring
• Behavior changes

Exceptions (ask your human partner):

• Throwaway prototypes
• Generated code
• Configuration files

Thinking "skip TDD just this once"? Stop. That's rationalization.

The Iron Law

NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST

Write code before the test? Delete it. Start over.

No exceptions:

• Don't keep it as "reference"
• Don't "adapt" it while writing tests
• Don't look at it
• Delete means delete

Implement fresh from tests. Period.

Expanded examples and anti-pattern rationale live in $_FEATUREFORGE_ROOT/references/debugging-tdd-examples.md.

Red-Green-Refactor

RED - Write Failing Test

Write one minimal test showing what should happen.

Requirements:

• One behavior
• Clear name
• Real code (no mocks unless unavoidable)

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)

Test passes? You're testing existing behavior. Fix test.

Test errors? Fix error, re-run until it fails correctly.

GREEN - Minimal Code

Write simplest code to pass the test.

Don't add features, refactor other code, or "improve" beyond the test.

Verify GREEN - Watch It Pass

MANDATORY.

npm test path/to/test.test.ts

Confirm:

• Test passes
• Other tests still pass
• Output pristine (no errors, warnings)

Test fails? Fix code, not test.

Other tests fail? Fix now.

REFACTOR - Clean Up

After green only:

• Remove duplication
• Improve names
• Extract helpers

Keep tests green. Don't add behavior.

Repeat

Next failing test for next feature.

Red Flags - STOP and Start Over

• Code before test
• Test after implementation
• Test passes immediately
• Can't explain why test failed
• Tests added "later"
• Rationalizing "just this once"
• "I already manually tested it"
• "Tests after achieve the same purpose"
• "It's about spirit not ritual"
• "Keep as reference" or "adapt existing code"
• "Already spent X hours, deleting is wasteful"
• "TDD is dogmatic, I'm being pragmatic"
• "This is different because..."

All of these mean: Delete code. Start over with TDD.

Verification Checklist

Before marking work complete:

• Every new function/method has a test
• Watched each test fail before implementing
• Each test failed for expected reason (feature missing, not typo)
• Wrote minimal code to pass each test
• All tests pass
• Output pristine (no errors, warnings)
• Tests use real code (mocks only if unavoidable)
• Edge cases and errors covered

Can't check all boxes? You skipped TDD. Start over.

Debugging Integration

Bug found? Write failing test reproducing it. Follow TDD cycle. Test proves fix and prevents regression.

Never fix bugs without a test.

Testing Anti-Patterns

When adding mocks or test utilities, read skill-local testing-anti-patterns.md to avoid common pitfalls:

• Testing mock behavior instead of real behavior
• Adding test-only methods to production classes
• Mocking without understanding dependencies

Final Rule

Production code → test exists and failed first
Otherwise → not TDD

No exceptions without your human partner's permission.