i need to export my functions from index.js
And use it in app.js
like
myFunction()
Dont
var.myFunction()
And whithout using
{myFunction} = require("index.js")
Because i need import them all
Assign all functions in index.js to module.exports
for example , below content in your index.js
module.exports= { t: x=> console.log ('this is '+x), add: (x,y) => x+y}
to import them use
const myFunctions =require('index.js')
and then you can call
myFunctions.add(2,3)
To learn more check module.exports in : https://learnjsx.com/category/2/posts/es6-moduleExports
Please learn more about the CommonJS module specification.
https://flaviocopes.com/commonjs/
Let's assume we have util.js.
exports.one = () => {}
exports.two = () => {}
exports.three = () => {}
Then as I know we can import everything like this.
const Util = require('utils.js');
Util.one()
Util.two()
Util.three()
Using ES6 syntax
import * as Util from 'utils.js'
Hope that answers your question.
I want to test that my third-party-library (iframe-resizer) function is called.
My test
import React from 'react';
import { fireEvent, render } from 'react-testing-library';
//import * as depModule from 'iframe-resizer';
let depModule = require("iframe-resizer")
import { MyComponent } from '../my-component';
describe('Component', () => {
describe('Functional', () => {
it('should initialize iframeresizer when the iframe has loaded', async
() => {
const iframeResizerMock = jest.spyOn(depModule, "iframeResizer");
const { queryByTestId } = render(<MyComponent />);
fireEvent.load(queryByTestId('csb-iframe'));
expect(iframeResizerMock).toHaveBeenCalledTimes(1);
});
});
});
So the iframeResizer function is called,it was tested by console.log.The strange thing here is when I use
import * as depModule from 'iframe-resizer';
The spyon doesn't work(test fails)
But when I use
let depModule = require("iframe-resizer")
Everything works great(test passes) . I'm new in jest and node modules,so may be I missed simething obvious?
This happens because jest's mocking only works for commonjs modules, and in your case iframe-resizer does not ship commonjs modules, and jest does not transform node modules to commonjs.
Take a look at this thread. There are many interesting solutions in there.
I am having a problem whereby if I export * from submodule (using ES6 module syntax and babel) I am unable to mock the submodules functions using Jest from the entry point. I wondered if anyone out there could help...
For example given this structure:
+ __tests__
| |- index.js
+ greeter
| |- index.js
| |- submodule.js
|- index.js
And this code:
index.js
import { sayHello } from "./greeter";
export const greet = (name) => sayHello(name);
greeter/index.js
export * from "./submodule.js";
greeter/submodule.js
export const sayHello = (name) => console.log(`Hello, ${name}`);
__tests__/index.js
import { greet } from "../index";
import * as greeter from "../greeter";
describe("greet", () => {
it("Should delegate the call to greeter.sayHello", () => {
const name = "John";
greet(name);
});
});
This all works fine and when the test runs it passes. Hello, John is printed to the console as expected. The advantage that make this worth it to me is that index.js is completely unaware of the structure of the greeter module, so i can restructure and refactor that code without worrying about my consumers.
The Rub comes when I try and mock out greeter.sayHello...
__tests__/index.js
import { greet } from "../index.js";
import * as greeter from "../greeter";
greeter.sayHello = jest.fn();
describe("greet", () => {
it("Should delegate the call to greeter.sayHello", () => {
const name = "John";
greet(name);
expect(greeter.sayHello).toHaveBeenCalledWith(name);
});
});
Now instead of the test passing as expected - I get an error:
Test suite failed to run
TypeError: Cannot set property sayHello of [object Object] which only has a getter
...(stack trace)
Changing the greeter import in __tests__/index.js to:
import * as greeter from "../greeter/submodule";
Makes the test pass but puts the coupling back in my test code.
Is there another way?
In order to mock a imported method on the file you want to test you need make sure the mock ran before you import your file(index.js), like this:
// import { greet } from "../index.js"; =====> Import on each test case(it)
// import * as greeter from "../greeter"; =====> Mock on each test case(it)
// greeter.sayHello = jest.fn(); =====> Would be not good to do this, it will mess with the entire import and this jest.fn will be share across your tests making it gives you false positives.
describe("greet", () => {
it("Should delegate the call to greeter.sayHello", () => {
const name = "John";
jest.mock('../greeter', () => ({ sayHello: jest.fn() })); // here you mock the import, remember it needs to be before you require your index.js
const greet = require('../index.js').greet; // require after the mock
greet(name);
expect(greeter.sayHello).toHaveBeenCalledWith(name);
});
});
I am trying to spy on RxJS operators with Jasmine. There are different use cases in my tests where I want to be in control on what a Observable returns. To illustrate what I am trying to do I have created the example above even thought it does not make to much sense as this observable always returns the same hard coded string. Anyway it is a good example to show what I am trying to achieve:
Imagine I have the following Class.
import {Observable} from 'rxjs/Observable';
import {of} from 'rxjs/observable/of';
export class AwesomeTest {
constructor() {
}
getHero(): Observable<string> {
return of('Spiderman');
}
}
And the following test:
import {AwesomeTest} from './awesomTest';
import {of} from 'rxjs/observable/of';
import createSpyObj = jasmine.createSpyObj;
import createSpy = jasmine.createSpy;
describe('Awesome Test', () => {
let sut;
beforeEach(() => {
sut = new AwesomeTest()
})
fit('must be true', () => {
// given
const expectedHero = 'Superman'
const asserter = {
next: hero => expect(hero).toBe(expectedHero),
error: () => fail()
}
createSpy(of).and.returnValue(of('Superman'))
// when
const hero$ = sut.getHero()
// then
hero$.subscribe(asserter)
});
});
I try to spy on the Observable of operator and return a Observable with a value that I specified inside my test instead of the actual value it will return. How can I achieve this?
Before the new Rx Import Syntax I was able to do something like this:
spyOn(Observable.prototype,'switchMap').and.returnValue(Observable.of(message))
In your spec file, everything as a wildcard (don't worry about tree shaking, this is just for the tests)
import * as rxjs from 'rxjs';
You can then use rxjs for your spying
spyOn(rxjs, 'switchMap').and.returnValue(rxjs.of(message))
I want to test that one of my ES6 modules calls another ES6 module in a particular way. With Jasmine this is super easy --
The application code:
// myModule.js
import dependency from './dependency';
export default (x) => {
dependency.doSomething(x * 2);
}
And the test code:
//myModule-test.js
import myModule from '../myModule';
import dependency from '../dependency';
describe('myModule', () => {
it('calls the dependency with double the input', () => {
spyOn(dependency, 'doSomething');
myModule(2);
expect(dependency.doSomething).toHaveBeenCalledWith(4);
});
});
What's the equivalent with Jest? I feel like this is such a simple thing to want to do, but I've been tearing my hair out trying to figure it out.
The closest I've come is by replacing the imports with requires, and moving them inside the tests/functions. Neither of which are things I want to do.
// myModule.js
export default (x) => {
const dependency = require('./dependency'); // Yuck
dependency.doSomething(x * 2);
}
//myModule-test.js
describe('myModule', () => {
it('calls the dependency with double the input', () => {
jest.mock('../dependency');
myModule(2);
const dependency = require('../dependency'); // Also yuck
expect(dependency.doSomething).toBeCalledWith(4);
});
});
For bonus points, I'd love to make the whole thing work when the function inside dependency.js is a default export. However, I know that spying on default exports doesn't work in Jasmine (or at least I could never get it to work), so I'm not holding out hope that it's possible in Jest either.
Edit: Several years have passed and this isn't really the right way to do this any more (and probably never was, my bad).
Mutating an imported module is nasty and can lead to side effects like tests that pass or fail depending on execution order.
I'm leaving this answer in its original form for historical purposes, but you should really use jest.spyOn or jest.mock. Refer to the jest docs or the other answers on this page for details.
Original answer follows:
I've been able to solve this by using a hack involving import *. It even works for both named and default exports!
For a named export:
// dependency.js
export const doSomething = (y) => console.log(y)
// myModule.js
import { doSomething } from './dependency';
export default (x) => {
doSomething(x * 2);
}
// myModule-test.js
import myModule from '../myModule';
import * as dependency from '../dependency';
describe('myModule', () => {
it('calls the dependency with double the input', () => {
dependency.doSomething = jest.fn(); // Mutate the named export
myModule(2);
expect(dependency.doSomething).toBeCalledWith(4);
});
});
Or for a default export:
// dependency.js
export default (y) => console.log(y)
// myModule.js
import dependency from './dependency'; // Note lack of curlies
export default (x) => {
dependency(x * 2);
}
// myModule-test.js
import myModule from '../myModule';
import * as dependency from '../dependency';
describe('myModule', () => {
it('calls the dependency with double the input', () => {
dependency.default = jest.fn(); // Mutate the default export
myModule(2);
expect(dependency.default).toBeCalledWith(4); // Assert against the default
});
});
You have to mock the module and set the spy by yourself:
import myModule from '../myModule';
import dependency from '../dependency';
jest.mock('../dependency', () => ({
doSomething: jest.fn()
}))
describe('myModule', () => {
it('calls the dependency with double the input', () => {
myModule(2);
expect(dependency.doSomething).toBeCalledWith(4);
});
});
Fast forwarding to 2020, I found this blog post to be the solution: Jest mock default and named export
Using only ES6 module syntax:
// esModule.js
export default 'defaultExport';
export const namedExport = () => {};
// esModule.test.js
jest.mock('./esModule', () => ({
__esModule: true, // this property makes it work
default: 'mockedDefaultExport',
namedExport: jest.fn(),
}));
import defaultExport, { namedExport } from './esModule';
defaultExport; // 'mockedDefaultExport'
namedExport; // mock function
Also one thing you need to know (which took me a while to figure out) is that you can't call jest.mock() inside the test; you must call it at the top level of the module. However, you can call mockImplementation() inside individual tests if you want to set up different mocks for different tests.
To mock an ES6 dependency module default export using Jest:
import myModule from '../myModule';
import dependency from '../dependency';
jest.mock('../dependency');
// If necessary, you can place a mock implementation like this:
dependency.mockImplementation(() => 42);
describe('myModule', () => {
it('calls the dependency once with double the input', () => {
myModule(2);
expect(dependency).toHaveBeenCalledTimes(1);
expect(dependency).toHaveBeenCalledWith(4);
});
});
The other options didn't work for my case.
Adding more to Andreas' answer. I had the same problem with ES6 code, but I did not want to mutate the imports. That looked hacky. So I did this:
import myModule from '../myModule';
import dependency from '../dependency';
jest.mock('../dependency');
describe('myModule', () => {
it('calls the dependency with double the input', () => {
myModule(2);
});
});
And added file dependency.js in the " __ mocks __" folder parallel to file dependency.js. This worked for me. Also, this gave me the option to return suitable data from the mock implementation. Make sure you give the correct path to the module you want to mock.
The question is already answered, but you can resolve it like this:
File dependency.js
const doSomething = (x) => x
export default doSomething;
File myModule.js
import doSomething from "./dependency";
export default (x) => doSomething(x * 2);
File myModule.spec.js
jest.mock('../dependency');
import doSomething from "../dependency";
import myModule from "../myModule";
describe('myModule', () => {
it('calls the dependency with double the input', () => {
doSomething.mockImplementation((x) => x * 10)
myModule(2);
expect(doSomething).toHaveBeenCalledWith(4);
console.log(myModule(2)) // 40
});
});
None of the answers here seemed to work for me (the original function was always being imported rather than the mock), and it seems that ESM support in Jest is still work in progress.
After discovering this comment, I found out that jest.mock() does not actually work with regular imports, because the imports are always run before the mock (this is now also officially documented). Because of this, I am importing my dependencies using await import(). This even works with a top-level await, so I just have to adapt my imports:
import { describe, expect, it, jest } from '#jest/globals';
jest.unstable_mockModule('../dependency', () => ({
doSomething: jest.fn()
}));
const myModule = await import('../myModule');
const dependency = await import('../dependency');
describe('myModule', async () => {
it('calls the dependency with double the input', () => {
myModule(2);
expect(dependency.doSomething).toBeCalledWith(4);
});
});
I solved this another way. Let's say you have your dependency.js
export const myFunction = () => { }
I create a depdency.mock.js file besides it with the following content:
export const mockFunction = jest.fn();
jest.mock('dependency.js', () => ({ myFunction: mockFunction }));
And in the test, before I import the file that has the dependency, I use:
import { mockFunction } from 'dependency.mock'
import functionThatCallsDep from './tested-code'
it('my test', () => {
mockFunction.returnValue(false);
functionThatCallsDep();
expect(mockFunction).toHaveBeenCalled();
})
I tried all the solutions and none worked or were showing lots of TS errors.
This is how I solved it:
format.ts file:
import camelcaseKeys from 'camelcase-keys'
import parse from 'xml-parser'
class Format {
parseXml (xml: string) {
return camelcaseKeys(parse(xml), {
deep: true,
})
}
}
const format = new Format()
export { format }
format.test.ts file:
import format from './format'
import camelcaseKeys from 'camelcase-keys'
import parse from 'xml-parser'
jest.mock('xml-parser', () => jest.fn().mockReturnValue('parsed'))
jest.mock('camelcase-keys', () => jest.fn().mockReturnValue('camel cased'))
describe('parseXml', () => {
test('functions called', () => {
const result = format.parseXml('XML')
expect(parse).toHaveBeenCalledWith('XML')
expect(camelcaseKeys).toHaveBeenCalledWith('parsed', { deep: true })
expect(result).toBe('camel cased')
})
})
I made some modifications on #cam-jackson original answer and side effects has gone. I used lodash library to deep clone the object under test and then made any modification I want on that object. But be ware that cloning heavy objects can have negative impact on test performance and test speed.
objectUndertest.js
const objectUnderTest = {};
export default objectUnderTest;
objectUnderTest.myFunctionUnterTest = () => {
return "this is original function";
};
objectUndertest.test.js
import _ from "lodash";
import objectUndertest from "./objectUndertest.js";
describe("objectUndertest", () => {
let mockObject = objectUndertest;
beforeEach(() => {
mockObject = _.cloneDeep(objectUndertest);
});
test("test function", () => {
mockObject.myFunctionUnterTest = () => {
return "this is mocked function.";
};
expect(mockObject.myFunctionUnterTest()).toBe("this is mocked function.");
});
});