@suspensive/react/src/hooks/usePrevious.spec.ts

Suspensive interfaces for react

import { renderHook } from '@testing-library/react'
import { usePrevious } from './usePrevious'

describe('usePrevious', () => {
  it('should return value given as an argument in the previous rendering', () => {
    const { result, rerender } = renderHook<{ now: number; prev: number }, { count: number }>(
      ({ count }) => ({ prev: usePrevious(count), now: count }),
      { initialProps: { count: 0 } }
    )

    rerender({ count: 1 })
    expect(result.current.prev).toBe(0)
    expect(result.current.now).toBe(1)

    rerender({ count: 2 })
    expect(result.current.prev).toBe(1)
    expect(result.current.now).toBe(2)

    rerender({ count: 3 })
    expect(result.current.prev).toBe(2)
    expect(result.current.now).toBe(3)
  })
})