Javascript 开玩笑预期已调用模拟函数，但未调用该函数

假设我有MyFile.js

export const test2 = () => {}
export const test = () => {
  test2();
}

然后我有了MyFile.test.js：

import * as MyFile from "./MyFile";

it("when test() is called should call test2", () => {
  const spy = jest.spyOn(MyFile, "test2");
  MyFile.test();
  expect(spy).toHaveBeenCalled();
})

为什么调用了错误

预期的模拟函数，但在这种情况下没有调用它？

将对象的属性包装在spy中

MyFile

表示从

MyFile.js

so

jest.spyOn（MyFile，“test2”）导出的模块将
test2
的模块导出包装在间谍文件中

…但是当调用
MyFile.test
时，它会直接调用
test2
，因此间谍永远不会被调用


修复它的一种方法是将
test2
移动到它自己的模块中：

MyFile.js

export const test2 = () => {}
export const test = () => {
  test2();
}

import { test2 } from './OtherModule';

export const test = () => {
  test2();
}

import * as MyFile from './MyFile';  // <= import module bindings

export const test2 = () => {}
export const test = () => {
  MyFile.test2();  // <= call the module export for test2
}

OtherModule.js

export const test2 = () => {}

MyFile.test.js

import * as MyFile from "./MyFile";
import * as OtherModule from "./OtherModule";

it("when test() is called should call test2", () => {
  const spy = jest.spyOn(OtherModule, "test2");
  MyFile.test();
  expect(spy).toHaveBeenCalled();  // Success!
})

import * as MyFile from "./MyFile";

it("when test() is called should call test2", () => {
  const spy = jest.spyOn(MyFile, "test2");
  MyFile.test();
  expect(spy).toHaveBeenCalled();  // Success!
})


另一种方法是导入模块绑定，这样您就可以为
test2
调用模块导出：

MyFile.js

export const test2 = () => {}
export const test = () => {
  test2();
}

import { test2 } from './OtherModule';

export const test = () => {
  test2();
}

import * as MyFile from './MyFile';  // <= import module bindings

export const test2 = () => {}
export const test = () => {
  MyFile.test2();  // <= call the module export for test2
}