describe('Applicative validation', () => {
  it('validates correct user', () => {
    const result = validateUser('Alice', 'alice@example.com', 25)
    expect(result._tag).toBe('Right')
    if (result._tag === 'Right') {
      expect(result.right).toEqual({ name: 'Alice', email: 'alice@example.com', age: 25 })
    }
  })

  it('accumulates all validation errors', () => {
    const result = validateUser('A', 'invalid', 16)
    expect(result._tag).toBe('Left')
    if (result._tag === 'Left') {
      expect(result.left.length).toBe(3) // All three validations failed
      expect(result.left).toContain('Name too short')
      expect(result.left).toContain('Invalid email')
      expect(result.left).toContain('Must be 18 or older')
    }
  })

  it('accumulates partial errors', () => {
    const result = validateUser('Alice', 'invalid', 25)
    expect(result._tag).toBe('Left')
    if (result._tag === 'Left') {
      expect(result.left.length).toBe(1)
    }
  })
})