react-haiku/dist/tests/hooks/usePrevious.test.js

React Hook & Utility Library

import { renderHook, act } from '@testing-library/react';
import { usePrevious } from "../../hooks/usePrevious";
describe('usePrevious Hook', () => {
    test('returns the initial value initially', () => {
        const initialValue = "initial";
        const { result } = renderHook(() => usePrevious(initialValue));
        expect(result.current).toBe(initialValue);
    });
    test('returns the previous value', () => {
        const initialValue = "initial";
        const { result, rerender } = renderHook(({ value }) => usePrevious(value), {
            initialProps: {
                value: initialValue
            }
        });
        expect(result.current).toBe(initialValue);
        act(() => {
            rerender({ value: "previous" });
        });
        expect(result.current).toBe(initialValue);
        act(() => {
            rerender({ value: "next" });
        });
        expect(result.current).toBe("previous");
    });
});