如何模拟作为参数传递的回调调用？

Question

我想知道如何模拟作为参数传递的回调调用：type YesOrNoHandler = (yesOrNo: boolean) => voidtype CheckValue = (val: string, handler: YesOrNoHandler)在这个例子中，我想模拟参数的调用handler: YesOrNoHandler，它代表一个回调。const check = jest.fn().mockImplementation((_, handler) => {   handler(true) // how to call `handler` outside of this scope ?})实际上，我什至不确定我是否必须为此开玩笑。有人知道如何实现这一目标吗？

Answer 1

只需将 分配给handler外部定义的变量。

例如

describe('61504714', () => {

  it('should pass', () => {

    let handlerRef;

    const check = jest.fn().mockImplementation((_, handler) => {

      console.log('call check');

      handlerRef = handler;

    });

    const callback = jest.fn((yesOrNo: boolean) => (yesOrNo ? 'yes' : 'no'));

    check('_', callback);

    expect(callback).not.toBeCalled();

    const rval = handlerRef(true);

    expect(rval).toBe('yes');

    expect(check).toBeCalledWith('_', callback);

    expect(callback).toBeCalledWith(true);

  });

});

试验结果：

 PASS  stackoverflow/61504714/index.test.ts (11.463s)

  61504714

    ✓ should pass (33ms)

  console.log stackoverflow/61504714/index.test.ts:5

    call check

Test Suites: 1 passed, 1 total

Tests:       1 passed, 1 total

Snapshots:   0 total

Time:        13.581s