planning-patterns

Writing Plans

Overview

Write comprehensive implementation plans assuming the engineer has zero context for the codebase and questionable taste. Document everything they need to know: which files to touch for each task, code, testing, docs they might need to check, how to test it. Give them the whole plan as bite-sized tasks. DRY. YAGNI. TDD. Frequent commits.

Assume they are a skilled developer, but know almost nothing about the toolset or problem domain. Assume they don't know good test design very well.

Core principle: Plans must be executable without asking questions.

The Iron Law

NO VAGUE STEPS - EVERY STEP IS A SPECIFIC ACTION

"Add validation" is not a step. "Write test for empty email, run it, implement check, run it, commit" - that's 5 steps.

Bite-Sized Task Granularity

Each step is one action (2-5 minutes):

• "Write the failing test" - step
• "Run it to make sure it fails" - step
• "Implement the minimal code to make the test pass" - step
• "Run the tests and make sure they pass" - step
• "Commit" - step

Not a step:

• "Add authentication" (too vague)
• "Implement the feature" (multiple actions)
• "Test it" (which tests? how?)

Plan Document Header

Every plan MUST start with this header:

# [Feature Name] Implementation Plan

> **For Claude:** REQUIRED: Follow this plan task-by-task using TDD.
> **Design:** See `docs/plans/YYYY-MM-DD-<feature>-design.md` for full specification.

**Goal:** [One sentence describing what this builds]

**Architecture:** [2-3 sentences about approach]

**Tech Stack:** [Key technologies/libraries]

**Prerequisites:** [What must exist before starting]

---

If a design document exists, always reference it in the header.

Task Structure

### Task N: [Component Name]

**Files:**
- Create: `exact/path/to/file.ts`
- Modify: `exact/path/to/existing.ts:123-145`
- Test: `tests/exact/path/to/test.ts`

**Step 1: Write the failing test**

```typescript
test('specific behavior being tested', () => {
  const result = functionName(input);
  expect(result).toBe(expected);
});

Step 2: Run test to verify it fails

Run: npm test tests/path/test.ts -- --grep "specific behavior" Expected: FAIL with "functionName is not defined"

Step 3: Write minimal implementation

function functionName(input: InputType): OutputType {
  return expected;
}

Step 4: Run test to verify it passes

Run: npm test tests/path/test.ts -- --grep "specific behavior" Expected: PASS

Step 5: Commit

git add tests/path/test.ts src/path/file.ts
git commit -m "feat: add specific feature"