Jest測試React Hooks的useMemo

useMemo 是 React Hooks 中的一個(gè)函數(shù)，它用于在組件之間緩存計(jì)算結(jié)果

以下是一個(gè)使用 useMemo 的簡單示例：

import React, { useState, useMemo } from 'react';

function MyComponent() {
  const [count, setCount] = useState(0);

  const doubleCount = useMemo(() => {
    return count * 2;
  }, [count]);

  return (
    <div>
      <p>Count: {count}</p>
      <p>Double Count: {doubleCount}</p>
     <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

export default MyComponent;

要使用 Jest 測試此組件，您需要首先安裝 @testing-library/react 和 @testing-library/jest-dom。然后，您可以編寫以下測試：

import React from 'react';
import { render, fireEvent, screen } from '@testing-library/react';
import MyComponent from './MyComponent';

describe('MyComponent', () => {
  it('should display the correct double count', () => {
    render(<MyComponent />);

    // Check initial state
    expect(screen.getByText('Count: 0')).toBeInTheDocument();
    expect(screen.getByText('Double Count: 0')).toBeInTheDocument();

    // Increment count
    fireEvent.click(screen.getByText('Increment'));

    // Check updated state
    expect(screen.getByText('Count: 1')).toBeInTheDocument();
    expect(screen.getByText('Double Count: 2')).toBeInTheDocument();
  });
});

這個(gè)測試將確保 useMemo 正確地計(jì)算了 doubleCount。當(dāng)然，這只是一個(gè)簡單的示例，實(shí)際上您可能需要根據(jù)您的需求編寫更復(fù)雜的測試。但是，這應(yīng)該為您提供了一個(gè)很好的起點(diǎn)來測試使用 useMemo 的 React Hooks。