开玩笑：测试内部函数称为

Question

鉴于以下情况，当执行foo函数时，如何确保使用正确的消息调用内部bar函数？谢谢。

const foo = (message) => console.log(message);

const bar = () => foo('this is a message');

test('test that the foo function is called with the correct message when the bar' +
     ' function is executed', () => {
  bar();
  expect(foo).toHaveBeenCalledWith('this is a message');
});

Answer 1

您需要像这样模拟foo函数：

let foo = message => console.log(message)

const bar = () => foo('this is a message')

test('test that the foo function is called with the correct message when the bar function is executed', () => {
    foo = jest.fn()
    bar()
    expect(foo).toHaveBeenCalledWith('this is a message')
})