tdd-workflow

TDD Workflow Skill

Automatically enforce Test-Driven Development practices during implementation.

When to Activate

• When /cdf:tdd command is invoked
• During feature implementation when user mentions "TDD", "test-first", or "test-driven"
• When implementing bug fixes that should start with a failing test
• During any implementation where high code quality is required

Core Principles

RED-GREEN-REFACTOR Cycle

RED:      Write a failing test
GREEN:    Make it pass with minimal code
REFACTOR: Improve the code, keep tests green

Workflow Steps

1. Understand the Requirement

Before writing any code:

• Clarify what behavior needs to be implemented
• Identify inputs and expected outputs
• Break down into small, testable units

2. Write the Failing Test (RED)

// Start with the test
describe('calculateShippingCost', () => {
  it('should return free shipping for orders over $100', () => {
    const order = { total: 150, items: [] };
    const result = calculateShippingCost(order);
    expect(result).toBe(0);
  });
});

3. Run and See It Fail

npm test -- --testPathPattern="shipping"

# Expected output:
# FAIL  src/shipping.test.ts
# ● calculateShippingCost › should return free shipping for orders over $100
#   ReferenceError: calculateShippingCost is not defined

4. Write Minimal Implementation (GREEN)

// Minimal code to pass
function calculateShippingCost(order: Order): number {
  if (order.total > 100) {
    return 0;
  }
  return 10;
}

5. Run and See It Pass

npm test -- --testPathPattern="shipping"

# Expected output:
# PASS  src/shipping.test.ts
# ✓ calculateShippingCost › should return free shipping for orders over $100

6. Refactor If Needed (REFACTOR)

// Improved version with constants
const FREE_SHIPPING_THRESHOLD = 100;
const STANDARD_SHIPPING_COST = 10;

function calculateShippingCost(order: Order): number {
  return order.total > FREE_SHIPPING_THRESHOLD
    ? 0
    : STANDARD_SHIPPING_COST;
}