Lumina

Manuals / AI Coding with Cursor / Ch 6

B · Review & TestIntermediate35 min read

6. Test-driven prompting

AI Coding with Cursor · 44 pages source format

Write tests first, then ask the agent to make them pass. TDD + AI = fewer hallucinated implementations.

What you'll learn

  • TDD with agents
  • Test-first briefs
  • Red-green-refactor

Test-first workflow

1) Write failing test. 2) Brief agent: "Make this test pass. Do not change the test." 3) Review. 4) Refactor.

// You write this test first:
import { describe, it, expect } from 'vitest'
import { formatCurrency } from './format'

describe('formatCurrency', () => {
  it('formats USD with 2 decimals', () => {
    expect(formatCurrency(1234.5, 'USD')).toBe('$1,234.50')
  })
  it('handles zero', () => {
    expect(formatCurrency(0, 'USD')).toBe('$0.00')
  })
})

// Then brief agent: "Implement formatCurrency to pass these tests."

Do this now

Write a failing test for a utility function. Agent makes it pass.

Clear?

Guard the test file

Tell agent explicitly: "Do not modify test files." Prevents cheated passes.

Do this now

Run test-first workflow on 2 functions.

Clear?

Checklist