检查方法调用（私人/非出口）函数的ReWire可见

Question

我只有一个导出函数和一些非出口者的模块，以保持API的“干净”。我试图用玩笑来编写单元测试和要求，但出现以下错误：

Error: expect(jest.fn())[.not].toBeCalledTimes()
    jest.fn() value must be a mock function or spy.
Received:
    function: [Function doMagic]

我怎样才能得到笑话窥视这是通过rewire可见非出口法（一些其他的方式或者验证的方法调用频率），如果我试图窥探尽管能够调用函数中我得到这个错误如下图所示最后一次测试：Cannot spy the doMagic property because it is not a function; undefined given instead

我的方案的简单例子：eg.functions.js

const moreFunctions = require("./moreFunctions");

const theExportedFunction = someNumber => {
  return doMagic(someNumber);
};

function doMagic(someNumber) {
  if (someNumber % 2 === 0) {
    return moreFunctions.getTrue();
  }
  return moreFunctions.getFalse();
}

module.exports = { theExportedFunction };

其他模块：moreFunctions.js

const moreFunctions = {
  getTrue: () => true,
  getFalse: () => false
};

module.exports = moreFunctions;

如何我想测试一下：functions.test.js

const rewire = require("rewire");

const functions = rewire("./functions");
const moreFunctions = functions.__get__('moreFunctions');

const doMagic = functions.__get__('doMagic');

const getFalse = jest.spyOn(moreFunctions, 'getFalse');
const getTrue = jest.spyOn(moreFunctions, 'getTrue');

describe("testing inner functions ", () => {

  afterEach(() => {
    jest.clearAllMocks();
  });

  test('theExportedFunction calls doMagic with 1 returns false and does not call getTrue', () => {
    const result = functions.theExportedFunction(1);
    console.log('result: ' + result);
    expect(result).toBe(false);

    //expect(doMagic).toBeCalledTimes(1);  // this blows up
    expect(getTrue).toHaveBeenCalledTimes(0);
    expect(getFalse).toHaveBeenCalledTimes(1);
  });

  test('theExportedFunction calls doMagic with 2 returns true and does not call getFalse', () => {
    const result = functions.theExportedFunction(2);
    console.log('result: ' + result);
    expect(result).toBe(true);

    //expect(doMagic).toBeCalledTimes(1); // this blows up
    expect(getTrue).toHaveBeenCalledTimes(1);
    expect(getFalse).toHaveBeenCalledTimes(0);
  });

  // This works!
  test('just testing to see if i can call the doMagic function', () => {
    const result = doMagic(2);
    expect(result).toBe(true);

    expect(getTrue).toHaveBeenCalledTimes(1);
    expect(getFalse).toHaveBeenCalledTimes(0);
  });
});

Answer 1

鉴于你的代码，你应该能够嘲笑所有和测试theExportedFunction如下：

const mockGetTrue = jest.fn().mockReturnValue(true); // this name MUST start with mock prefix
const mockGetFalse = jest.fn().mockReturnValue(false); // this name MUST start with mock prefix
jest.spyOn('my_more_functions_path', () => ({
  getTrue: mockGetTrue,
  getFalse: mockGetFalse
}));
// here import the file you are testing, after the mocks! 
// for example
import {theExportedFunction} from 'my_path';

describe('theExportedFunction', () => {
  it('should call getTrue of moreFunctions', () => {
    theExportedFunction(4);
    expect(mockGetTrue).toHaveBeenCalled();
    expect(mockGetFalse).not.toHaveBeenCalled();
  });


  it('should call getFalse of moreFunctions', () => {
    theExportedFunction(5);
    expect(mockGetFalse).toHaveBeenCalled();
    expect(mockGetTrue).not.toHaveBeenCalled();
  });
});