诗农不存根于 module.exports

问题描述

如果创建一个包含以下内容的文件

If create an file with the following contents

const validateEmail = email => {
    sendEmail(email);
};

const sendEmail = email => {
  return true;
};

module.exports = {
  validateEmail,
  sendEmail,
};

还有一个试图剔除第二个函数的测试......

And a test that tries to stub out the second function...

it('Should call sendEmail if a valid email is passed', () => {
  let sendEmailSpy = sinon.stub(checkEmail, 'sendEmail');
  checkEmail.validateEmail('[email protected]');
  assert.isTrue(sendEmailSpy.called);
});

仍然调用了sendEmail函数，测试失败

It still calls the sendEmail function and the test fails

但是，如果我像这样编写 module.exports:

However, if I write the module.exports like this:

module.exports = {
  validateEmail(email) {
      this.sendEmail(email);
  },
  sendEmail(email) {
    return true;
  },
};

它正确地存根......为什么?

It stubs it correctly...Why?

推荐答案

简短回答 - 上下文

长答案 - 在第一种情况下，导出的 sendEmail 函数与 validateEmail 使用的内部函数不同.导出的函数成为被导出对象的一个​​新属性，并简单地引用内部的.

Long answer - in the first scenario, the exported sendEmail function is not the same as the internal one that is used by validateEmail. The exported function becomes a new property of the object being exported and simply references the internal one.

在第二种情况下，您在 validateEmail 的导出对象(即 this.sendEmail(...))上显式引用了 sendEmail 函数code> 因此它将使用存根版本.

In the second scenario, you explicitly reference the sendEmail function on the exported object (i.e. this.sendEmail(...)) from validateEmail therefore it will use the stubbed version.

这个故事的寓意——你不能把你看不到的东西置之不理.

Moral of the story - you can't stub something you can't see.

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