describe('Nested validation', () => {
  it('validates complete person with address', () => {
    const person = {
      name: 'Alice',
      address: { street: '123 Main St', city: 'Boston', zipCode: '02101' },
    }
    const result = validatePerson(person)
    expect(result._tag).toBe('Right')
  })

  it('accumulates errors from all levels', () => {
    const person = {
      name: '',
      address: { street: '', city: '', zipCode: '123' },
    }
    const result = validatePerson(person)
    expect(result._tag).toBe('Left')
    if (result._tag === 'Left') {
      expect(result.left.length).toBeGreaterThan(2) // Errors from both person and address
    }
  })
})