Javascript 模拟方法中的变量 [英] Javascript mock a variable inside a method

问题描述

我有这个对象:

import keys from './keys'
const obj = {
  getData: async funcion(url) {
    const key = await keys.getAccess()

    return get(url, {
        secret: key
      }
    })
}
}

我想用模拟值模拟 key 变量.我试过了:

I want to mock the key variable with a mock value. I tried:

test('test', async() => {
  const spyD = jest.spyOn(obj, 'getData');
  expect(obj.getData).toHaveBeenCalledWith('/url', {secret: 'my mocked key') //but secret is undefined
})

...但我不能模拟 key 变量.如何从我的函数中模拟该变量?

... but i can't mock the key variable. How to mock that variable from my function?

推荐答案

不能直接；范围已关闭，无法访问其中声明的变量.您可以传入创建 key 的函数，以便您可以模拟其实现，同时将原始函数作为默认值传递:

You can't directly; the scope is closed over, there is no way to gain access to a variable declared within it. You can pass in the function that creates key instead so that you can mock its implementation, while passing the original function as a default:

const obj = {
  getData: async function(url, getAccess = keys.getAccess) {
    const key = await getAccess()

    return get(url, {
        secret: key
      }
    })
  }
}

test('test', async () => {
  const spyD = jest.spyOn(obj, 'getData');

  const result = await obj.getData("/url", async () => "my mocked key");

  expect(spyD).toHaveBeenCalledWith("/url");
})

这个测试现在应该通过了，result 将是 get 的返回值，用 "/url" 和 调用{秘密:我的模拟密钥"}.

This test should now pass, and result will be the return value of get called with "/url" and {secret: "my mocked key"}.

或者，如果您不想修改obj，您可以完全模拟getData 的实现以获得相同的结果:

Alternatively, if you would prefer not to modify obj, you can mock the implementation of getData altogether to get the same result:

test('test', async () => {
  const spyD = jest.spyOn(obj, 'getData').mockImplementation(async (url) => {
    return get(url, {secret: "my-mocked-key"})
  });

  const result = await obj.getData("/url");

  expect(spyD).toHaveBeenCalledWith("/url");
})

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