jest.mock(module)和jest.fn()之间的区别是什么？

Question

我已经尝试了几种不同的方法来定义模拟函数,并且我的所有尝试都失败了.当我尝试将其定义如下:

jest.mock('../src/data/server', ()=> ({server: {report: jest.fn()}}));
expect(server.report.mock).toBeCalledWith(id, data, () => {...}, () => {...});

我收到这个错误:

expect(jest.fn())[.not].toBeCalledWith()
jest.fn() value must be a mock function or spy.
Received: undefined

如果我将模拟定义为:

var spy = jest.mock('../src/data/server', ()=> ({server: {report: jest.fn()}}));
expect(spy).toBeCalledWith(id, data, () => {...}, () => {...});

它返回以下错误:

    expect(jest.fn())[.not].toBeCalledWith()
    jest.fn() value must be a mock function or spy.
    Received:
      object: {"addMatchers": [Function anonymous], "autoMockOff": [Function anonymous], "autoMockOn": [Function anonymous], "clearAllMocks": [Function anonymous], "clearAllTimers": [Function anonymous], "deepUnmock": [Function anonymous], "disableAutomock": [Function anonymous], "doMock": [Function anonymous], "dontMock": [Function anonymous], "enableAutomock": [Function anonymous], "fn": [Function anonymous], "genMockFn": [Function bound getMockFunction], "genMockFromModule": [Function anonymous], "genMockFunction": [Function bound getMockFunction], "isMockFunction": [Function isMockFunction],
 "mock": [Function anonymous], "resetModuleRegistry": [Function anonymous], "resetModules": [Function anonymous], "runAllImmediates": [Function anonymous], "runAllTicks": [Function anonymous], "runAllTimers": [Function anonymous], "runOnlyPendingTimers": [Function anonymous], "runTimersToTime": [Function anonymous],"setMock": [Function anonymous], "unmock": [Function anonymous], "useFakeTimers": [Function anonymous], "useRealTimers": [Function anonymous]}

作为我的第三次尝试,我将模拟定义为:

const st = require.requireActual('../src/data/server', ()=> ({server: {report: jest.fn()}}));
st.report = jest.fn();
expect(st.report).toBeCalledWith(id, data,  () => {...}, () => {...});

我收到这个错误:

expect(jest.fn()).toBeCalledWith(expected)
Expected mock function to have been called with:
  ["1033083fe", {"address": "test address", "affiliation": "testaaa", 
  "city": "testcity", "copyright": true, "country": "testcountry", "email": "sss@test.com", "message": "testmessage", 
  "name": "testname", "phone": "1234567890", "zipcode": "12345"}, [Function anonymous], [Function anonymous]]
But it was not called.

我想知道问题是什么以及这三种定义模拟的方式有何不同？

PS代码可以在这里找到:在Jest中为React表单编写单元测试

Answer 1

在第一个示例中,您说当模块'../src/data/server'在其他模块中导入时,它将是{server: {report: jest.fn()}}.在下一行中,您尝试使用server.问题是你永远不会导入你模拟的模块.您测试模块也许在server是{server: {report: jest.fn()}}在测试服务器,但你只是undefined因为你永远不导入.要解决这个问题,还必须导入它.

import server from '../src/data/server'
jest.mock('../src/data/server', ()=> ({server: {report: jest.fn()}}));
expect(server.report.mock).toBeCalledWith(id, data, () => {...}, () => {...});

在第二个例子中,它接缝就像jest.mock返回一样jest.

最后一个例子失败,因为你从不打电话st.report.

回到主要问题.jest.mock和之间的区别jest.fn

jest.mockjest.fn当只用path参数调用一个模块时,或者用函数的返回值替换一个模块,你可以将它作为第二个参数.因此,在您的第一个示例中,当您想要在其中一个文件中进行测试或在测试中进行测试时,'../src/data/server'它将被导入{server: {report: jest.fn()}}.

这给我们带来了什么jest.fn().这将返回一个间谍.间谍是一个功能,可以记住在其上进行的每个调用,以及使用哪些参数.

假设你有一个你想要测试的模块:

import server from './data/server'

server.report('test123')

要测试使用正确的参数进行此调用,您需要'./data/server'使用您可以控制的内容来模拟此依赖项.

import server from '../src/data/server'
import fileToTest from '../src/fileToTest'
jest.mock('../src/data/server', ()=> ({server: {report: jest.fn()}}));
expect(server.report.mock).toBeCalledWith('test123');

这里发生的是在所有导入内容开始之前jest替换 '../src/data/server'为你的模拟实现,所以当fileToTest导入服务器并调用它时,它实际上调用了spy函数.然后,您可以期望使用正确的参数调用它.

顺便说一句.您在测试中尝试检查功能,在调用间谍时传递的功能将不起作用,并且您传入的功能toBeCalledWith不相同.

在这种情况下,我会检查每个参数

expect(server.report.mock.calls[0][0]).toBe("1033083fe");
expect(server.report.mock.calls[0][0]).toEqual({"address": "test address", "affiliation": "testaaa", 
  "city": "testcity", "copyright": true, "country": "testcountry", "email": "sss@test.com", "message": "testmessage", 
  "name": "testname", "phone": "1234567890", "zipcode": "12345"});