2. Unit Testing. Hooks: useCounter

gistfile1.txt

// Hook
export const useCounter = (initialValue = 0) => {
  const [count, setCount] = useState(initialValue)
  
  const increment = () => setCount(c => c + 1)
  const decrement = () => setCount(c => c - 1)
  const reset = () => setCount(initialValue)
  
  return { count, increment, decrement, reset }
}

// Test
import { renderHook, act } from '@testing-library/react'

describe('useCounter', () => {
  it('inicia con el valor por defecto', () => {
    const { result } = renderHook(() => useCounter())
    expect(result.current.count).toBe(0)
  })

  it('inicia con valor personalizado', () => {
    const { result } = renderHook(() => useCounter(10))
    expect(result.current.count).toBe(10)
  })

  it('incrementa el contador', () => {
    const { result } = renderHook(() => useCounter())
    
    act(() => {
      result.current.increment()
    })
    
    expect(result.current.count).toBe(1)
  })

  it('resetea al valor inicial', () => {
    const { result } = renderHook(() => useCounter(5))
    
    act(() => {
      result.current.increment()
      result.current.increment()
      result.current.reset()
    })
    
    expect(result.current.count).toBe(5)
  })
})