I am mocking a library by doing this:
let helperFn;
let mock;
beforeEach(() => {
mock = jest.fn();
require('./helperFn').default = mock;
})
If I do this in a test, does it mean that from now on within the whole test suite that default function of helperFn will be associated with that mock?
In the Jest documentations I see how to reset the mock, but I don't see how to remove the mock from a required function. I am concerned that from that test on, all the calls into helperFn.default will see that mock.
ES6 modules
Here is an ES6 example:
helperFn.js
export default () => 'original';
code.js
import helperFn from './helperFn';
export const func = () => helperFn();
code.test.js
import * as helperFnModule from './helperFn';
import { func } from './code';
describe('helperFn mocked', () => {
let mock;
beforeEach(() => {
mock = jest.spyOn(helperFnModule, 'default');
mock.mockReturnValue('mocked');
});
afterEach(() => {
mock.mockRestore();
});
test('func', () => {
expect(func()).toBe('mocked'); // Success!
});
});
describe('helperFn not mocked', () => {
test('func', () => {
expect(func()).toBe('original'); // Success!
});
});
Details
Since ES6 imports are live views of the module exports, it is easy to mock an export and then restore it afterwards.
Node.js modules
Here is a Node.js example:
helperFn.js
exports.default = () => 'original';
code.js
const helperFn = require('./helperFn').default;
exports.func = () => helperFn();
code.test.js
describe('helperFn mocked', () => {
beforeEach(() => {
const helperFnModule = require('./helperFn');
helperFnModule.default = jest.fn(() => 'mocked');
});
afterEach(() => {
jest.resetModules();
});
test('func', () => {
const { func } = require('./code');
expect(func()).toBe('mocked'); // Success!
});
});
describe('helperFn not mocked', () => {
test('func', () => {
const { func } = require('./code');
expect(func()).toBe('original'); // Success!
});
});
Details
The default export gets remembered by code.js when it runs, so changing the default export of helperFn.js doesn't affect func once code.js is required. Jest also caches modules and returns the same module for multiple require calls unless jest.resetModules is called.
So for Node.js modules it is often easiest to require code within the test itself and use jest.resetModules to reset any mocking.
Related
I have following files and classes
//A.ts
export abstract class A{
protected abstract method1(arg){
}
}
// Session.ts
export class Session{
constructor(socket: WebSocket){
this._socket = socket;
this._socket.on('close', () => {do something} );
this._socket.on('error', () => {do something} );
this._socket.on('message', () => {do something} );
}
setSomeSocket(someSocket: WebSocket){
this._anotherSocket = someSocket;
this._anotherSocket.on('close', () => {do something} );
this._anotherSocket.on('error', () => {do something} );
};
}
// B.ts
export class B extends A{
protected async method1(arg){
try{
let tempSession = new Session();
tempSession.setSomeSocket(socket);
// do something with temp
}
catch(exception){
}
}
}
// B.spec.ts
describe("B test", () => {
it("some test", () => {
const varB = new B();
await varB["method1"](arg);
expect(spied).toBeCalledTimes(1);
});
})
I want to mock the class Session so that it doesn't create any problem in socket.on() methods. I am sending mocked websockets.
The class is external and I want the mock implementation inside test file such that when running the test, the mocked class gets called inside B.ts
You can mock directly with the jest:
jest.mock('./Session');
beforeEach(() => {
Session.mockClear();
})
Check out the manual mocking and auto mocking from Jest documentation.
As stated in another comment you can mock Session with jest
const mockSetSameSocks = jest.fn(); // note name starts with mock, important
jest.mock('./Session', () => {
return {
Session: jest.fn(() => ({
setSameSocks: mockSetSameSocks,
}))
}
});
// B.spec.ts
describe("B test", () => {
beforeEach(() => {
mockSetSameSocks.mockClear();
})
it("some test", () => {
const varB = new B();
await varB["method1"](arg);
expect(mockSetSameSocks).toBeCalledTimes(1);
});
})
I did the tests in the following way, but it bothers me how I need to import an object with the functions, instead of just importing the functions.
this works
//service.test.js
const get = require('../../modules/bankUser/model/getRegisteredUser');
get.getRegisteredUser = jest.fn()
.mockImplementationOnce(async () => mock)
.mockImplementationOnce(async () => mockUpdated);
//service.js
const get = require('../model/getRegisteredUser');
const testedFunction () => {
const depositReciver = await get.getRegisteredUser(depositName, depositCpf);
}
this dosent
//service.test.js
const get = require('../../modules/bankUser/model/getRegisteredUser');
get.getRegisteredUser = jest.fn()
.mockImplementationOnce(async () => mock)
.mockImplementationOnce(async () => mockUpdated);
//service.js
const { getRegisteredUser } = require('../model/getRegisteredUser');
const testedFunction () => {
const depositReciver = await getRegisteredUser(depositName, depositCpf);
}
I'm triyng this (way):
//service.test.js
const get = require('../../modules/bankUser/model/getRegisteredUser');
jest.mock('../../modules/bankUser/model/getRegisteredUser');
get.mockImplementationOnce(() => ({ getRegisteredUser: () => mockObject }));
jest returns this:
TypeError: get.mockImplementationOnce is not a function
also I've tried to import like this
//service.test.js
const { getRegisteredUser } = require('../../modules/bankUser/model/getRegisteredUser');
jest.mock('../../modules/bankUser/model/getRegisteredUser');
getRegisteredUser.mockImplementationOnce(() => ({ getRegisteredUser: () => mockObject }));
EDIT
//getRegisteredUser.js
const { getConnection } = require('../../../global/connection');
const getRegisteredUser = async (userName, cpf) => {
const db = await getConnection('Data-Base');
const res = await db.collection('Collection')
.findOne({ userName, cpf });
return res;
};
module.exports = { getRegisteredUser };
The example you are pointing [https://jestjs.io/docs/es6-class-mocks#replacing-the-mock-using-mockimplementation-or-mockimplementationonce][1]
is related to the default export but I think you are using named export in your code.
There are multiple ways to do so
One Way
const get = require('../../modules/bankUser/model/getRegisteredUser');
jest.mock('../../modules/bankUser/model/getRegisteredUser');
get.getRegisteredUser.mockImplementationOnce(() => mockObject);
Second Way
jest.mock('../../modules/bankUser/model/getRegisteredUser', () => ({
...jest.requireActual('../../modules/bankUser/model/getRegisteredUser'),
getRegisteredUser: jest.fn().mockImplementation(() => mockObject),
}))
An Another Way
We can also mock a module using the __mocks__ directory which is inbuilt feature of jest
And at the end never forgot to call clearAllMocks() after each test else it may impact the output of other tests.
afterEach(() => {
jest.clearAllMocks();
});
I have a module that exports a class and 2 functions and that module is imported into a file that is being tested.
someFile.js
const {theclass, thefunction} = require("theModule");
const getSomeFileData = () => {
let obj = new theclass();
//some logic
return obj.getData();
}
In the test file, I want to mock the module "theModule" and return a known value when the function obj.getData() is called. How would I go about mocking this module("theModule") when testing file "someFile.js"?
Edit:
.spec.ts
import { someFunction } from './index-test';
jest.mock('lodash', () => {
return {
uniqueId: () => 2,
};
});
describe('', () => {
it('', () => {
expect(someFunction()).toBe(2);
});
});
index-test.ts
import { uniqueId } from 'lodash';
export const someFunction = () => {
return uniqueId();
};
Is it possible to jest.spyOn a default export so that I can call the mockImplementation method to change what the function does before each test?
// code.js
module.exports = () => {
// some irrelevant code I want to rewrite with a mock
};
// test
const code = require('./code.js');
const mockCode = jest.spyOn(code, 'default'); // this line doesn't work with the error: "Cannot spy the default property because it is not a function; undefined given instead"
it('some test', async () => {
mockCode.mockImplementationOnce(() => { console.log('test') });
});
I've also tried to use jest.mock() unsuccessfully:
const code = require('./code');
jest.mock('./code',
() => () => {
console.log('test');
}
);
it('some test', async () => {
code.mockImplementationOnce(() => { console.log('test2') }); // error
});
I am having a hard time understanding what I am doing wrong.
I have a JS class as such:
export default class A {
constructor(repository) {
this._repository = repository;
}
async process(date) {
// ...
this._repository.writeToTable(entry);
}
}
and I am attempting to write a test that mocks the repository using sinon.mock
This is what I have so far:
describe('A', () => {
describe('#process(date)', () => {
it('should work', async () => {
const repository = { writeToTable: () => {} };
const mock = sinon.mock(repository);
const a = new A(repository);
await a.process('2017-06-16');
mock.expects('writeToTable').once();
mock.verify();
});
});
});
but it always fails saying that
ExpectationError: Expected writeToTable([...]) once (never called)
I've checked (added a console.log) and it is calling the object I defined on the test.
I ran this locally and read the documentation on sinonjs.org and you seem to be doing everything right.
I tried re-writing your example using a spy and ended up with something like this to get a passing test:
import sinon from "sinon";
import { expect } from "chai";
import A from "./index.js";
describe("A", () => {
describe("#process(date)", () => {
it("should work", async () => {
const repository = { writeToTable: sinon.spy() };
const a = new A(repository);
await a.process("2017-06-16");
expect(repository.writeToTable.calledOnce).to.be.true;
});
});
});