What is the difference between jest.mock (module) and jest.fn ()

Question

I tried a couple of different ways to define the mock function, and all my attempts failed. When I try to define it as follows:

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

I get this error:

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

If I define mock as:

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

it returns the following error:

    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]}

As a third attempt, I defined the layout as:

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

And I get this error:

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": "[e-mail]", "message": "testmessage", 
  "name": "testname", "phone": "1234567890", "zipcode": "12345"}, [Function anonymous], [Function anonymous]]
But it was not called.

I wonder what the problem is and how these three methods for defining the layout differ?

PS code can be found here: Write Unit test in Jest for the React form

Answer 1

, '../src/data/server' - , {server: {report: jest.fn()}}. server. , , . , , server, {server: {report: jest.fn()}}, undefined, . , .

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

jest.mock, jest.

st.report.

. jest.mock jest.fn

jest.mock jest.fn, , , . , , - , , '../src/data/server', {server: {report: jest.fn()}}.

jest.fn(). . - , .

, , :

import server from './data/server'

server.report('test123')

, , './data/server' , .

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');

, , , , '../src/data/server' , , fileToTest , . , .

Btw. , , , , , , , toBeCalledWith, .

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": "[e-mail]", "message": "testmessage", 
  "name": "testname", "phone": "1234567890", "zipcode": "12345"});