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Issue with setting up jest mock

I have the following function that is used within cypress tests for which I want to do unit testing (filterTests.js):
const filterTests = (definedTags, runTest) => {
console.log(`Cypress tags: ${definedTags}`);
let isFound = true;
const includeTag = Cypress.env('INCLUDETAG');
const excludeTag = Cypress.env('EXCLUDETAG');
if (includeTag) {
isFound = definedTags.includes(includeTag);
}
if (excludeTag) {
isFound = ! definedTags.includes(excludeTag);
}
if (isFound) {
runTest();
}
};
export default filterTests;
A test double for Cypress.env needs to be created. I'm not sure if this would technically be considered a stub, mock, fake, dummy, etc..., but the philosophical discussion isn't the focus right now. It looks like in the Cypress world, everything is lumped together under 'mock'.
I started down the path of something like this in the Jest test file:
import filterTests from '../../cypress/support/filterTests';
describe('Something', () => {
jest.mock('Cypress', () => ({
env: {
INCLUDETAG: 'jenkins1'
}
}));
it('Something else ', (done) => {
const tempFunc = () => {
console.log('here a');
done();
};
filterTests(tag, tempFunc);
});
});
But for that I get the error message:
Cannot find module 'Cypress' from 'spec/cypress/filterTestsSO2.test.js'
2 |
3 | describe('Something', () => {
> 4 | jest.mock('Cypress', () => ({
| ^
5 | env: {
6 | INCLUDETAG: 'jenkins1'
7 | }
I believe what is complicating this situation is that Cypress is not explicitly imported in filterTests.js

I think you might just want to set the env value at the top of the test
describe('Something', () => {
Cypress.env(INCLUDETAG, 'jenkins1')
it('Something else ', (done) => {
const tempFunc = () => {
console.log('here a');
done();
};
filterTests(tag, tempFunc); // this function will read the env set above
})
})
Further info - Cypress has a cy.spy() which wraps a method and records it's calls but otherwise leaves it's result the same.
Also cy.stub() which records calls but also provides a fake result.
Jest globals
If you are running the test in Jest, then the Cypress global should be able to be mocked simply by setting it up
global.Cypress = {
env: () => 'jenkins1' // or more complicated fn as test requires
}
Note I expect this will only work with simple cases. Cypress wraps jQuery, Chai and Mocha so they behave slightly differently when a Cypress test runs. If the function you test uses any of those features, even implicitly (like command retry), then Jest will not reproduce the right environment.
My recommendation, test Cypress with Cypress.

What's the proper type declaration of React context functions to avoid linting issues?

I am using React Context and I have:
const DocumentContext = createContext<
[DocumentStateType, React.Dispatch<any>, React.Dispatch<any>]
>([initVal, () => { }, () => { }]);
But my linter complains:
Unexpected empty arrow function #typescript-eslint/no-empty-function
I know I can turn that off in my linting settings, but is there a right way to do it?

If you're looking only to suppress linter message you may declare it as:
const DocumentContext = createContext<
[DocumentStateType, React.Dispatch<any>, React.Dispatch<any>]
>([initVal, () => { /* do nothing */ }, () => { /* do nothing */ }]);
or as:
const DocumentContext = createContext<
[DocumentStateType, React.Dispatch<any>, React.Dispatch<any>]
>([initVal, () => undefined, () => undefined]);
If you're absolutely sure you're not going to use this default value anywhere. i.e you don't have components using this context beyond this context's provider you may simply define it as:
const DocumentContext = createContext<
[DocumentStateType, React.Dispatch<any>, React.Dispatch<any>]
>(null as any);

You can use the option allowArrowFunctions
Documentation
"#typescript-eslint/no-empty-function": ["error", {"allow": ["arrowFunctions"]}],

Jasmine test case are failing, when testing setTimeout inside function [duplicate]

This question already has an answer here:
How to test code setup with babel configuration(For Library) using Jasmine?
(1 answer)
Closed 1 year ago.
Good Day Everyone,
I am quite new to testing frameworks Jasmine. We have a TS project setup and I am trying to test a function consisting of setTimeout, but it keeps failing. I am trying to use Clock
One Important point I noticed is that I am using babel-loader as soon as I change the webpack configuration to ts-loader. The test case doesn't fail. (Don't know Why 🤷‍♀️). I have checked multiple times but no luck.
UPDATE
I figured out why the test cases are failing but I have no idea why is it happening.
The configurations of babel and ts-loader are correct I just changed the setTimeout to window.setTimeout(in babel-loader) repository and now the test cases are executing successfully🤷‍♀️. This was just a wild guess from Stack Overflow Link.
I added a console statement of setTimeout and window.setTimeout and found that the definitions of both functions are very different. window.setTimeout has a definition(Green circle in the screenshot) that is the same as after we install Jasmine.clock install. ie. HERE
But setTimeout definition(Red circle in the screenshot) is very different(below).
function (/* ...args */) {
return fn.apply(that, arguments);
}
I tried doing the same in ts-loader repository but here setTimeout and window.setTimeout definitions are the same.
Code:
hideToast() {
setTimeout(() => {
this.showToast = false;
}, 5000);
}
Test Spec:
beforeEach(() => {
// Sometimes calling install() will fail for some reason,
// but calling uninstall() first will make it work
jasmine.clock().uninstall();
jasmine.clock().install();
});
afterEach(() => {
jasmine.clock().uninstall();
});
it('should hide toast', () => {
const obj: Car = new Car();
obj.showToast = true; // This value should change after timeout
obj.hideToast(); // Call the component method that turns the showToast value as false
jasmine.clock().tick(5000);
expect(obj.showToast).toBeFalsy(); // Then executes this
});
Any suggestion would be helpful.
With babel-loader(Test case fail's) Screenshot(Branch = "main"):
https://github.com/dollysingh3192/ts-babel-template
With ts-loader(Test cases passed) Screenshot(Branch = "tsloader"):
https://github.com/dollysingh3192/ts-babel-template/tree/tsloader

Example with clock() using a promise that we resolve straight away:
import { Car } from './car';
describe('Car', () => {
beforeEach(() => {
jasmine.clock().uninstall(); // you probably don't need this line
jasmine.clock().install();
});
afterEach(() => {
jasmine.clock().uninstall();
});
it('should hide toast', () => {
const obj: Car = new Car();
obj.showToast = true; // also here, it's redundant, as set to true in constructor
obj.hideToast();
Promise.resolve().then(() => {
jasmine.clock().tick(5000);
expect(obj.showToast).toBeFalsy();
});
});
});
Other ideas on how to do it in this github issue
But let's forget about the simple (and best solution) for a moment and dig a big into the issue. Without the Clock class, we would have to use the done() callback.
In that case, we would have two solutions:
1 - change jasmine.DEFAULT_TIMEOUT_INTERVAL, to be at least 1ms higher than your timeout:
import { Car } from './car';
describe('Car', () => {
beforeEach(() => {
jasmine.DEFAULT_TIMEOUT_INTERVAL = 5001;
});
it('should hide toast', (done) => {
const obj: Car = new Car();
obj.hideToast();
setTimeout(() => {
expect(obj.showToast).toBeFalsy();
done();
}, 5000)
});
});
This works with the done() callback (that might be used while working with async tasks)
and by overriding the jasmine.DEFAULT_TIMEOUT_INTERVAL.
2 - Lower your timeout - by 1 millisecond (yes, 1ms is enough):
import {Car} from './car';
describe('Car', () => {
it('go() works', () => {
const car: Car = new Car();
const returnValue = car.go('vroom');
expect(returnValue).toEqual('vroom');
});
it('should hide toast', (done) => {
const obj: Car = new Car();
obj.hideToast();
setTimeout(() => {
expect(obj.showToast).toEqual(false);
done();
}, 4999);
});
});
Same as before, done callback, but this time we finish 1 millisecond before the Jasmine default timeout and the test will pass (obviously, we need to do it in the class and in the test).
According to the Jasmine docs:

How to spy on multiple class/object methods with Jasmine

Is there a shorter way to spy on object methods than the following?
describe('blah blah', () => {
let localStorageSetSpy, localStorageGetSpy;
beforeEach(() => {
localStorageGetSpy = spyOn(window.localStorage, 'getItem');
localStorageSetSpy = spyOn(window.localStorage, 'setItem');
});
it('yada yada', () => {
// blah blah
})
})
It would be nice if I could spy on the getter and setter as part of the same object. I tried reassigning window.localStorage to jasmine.createSpyObj(...) but got complaints about it being readonly.
Any ideas?

If you just want to interact with one object in your test, maybe you can do this
describe('blah blah', () => {
const localStorageSpy = { getItem: undefined, setItem: undefined };
beforeEach(() => {
localStorageSpy.getItem = spyOn(window.localStorage, 'getItem');
localStorageSpy.setItem = spyOn(window.localStorage, 'setItem');
});
it('yada yada', () => {
localStorageSpy.getItem.mockReturnValue(...)
})
})

I would use some methods or functions to wrap around your window.localStorage operations. For example store() (which calls getItem) and retrieve() (which calls setItem).
Some benefits:
You will be able to spy on and mock said functions very easily.
In the future, you will be able to change the behaviour of these functions without having to care about what is done inside as long as the prototypes of store() and retrieve() stay the same.

describe('blah blah', () => {
const localStorageSpy = jasmine.createSpyObj('localStorage',['getItem','setItem']) // Jasmine automatically create a spy for you
beforeEach(() => {
});
it('yada yada', () => {
localStorageSpy.getItem = (() => { return mockReturnValue(...) }) // Do your test here.
})
})
Maybe you can try this. Jasmine createSpyObj will create spy for as well. However, for localStorage it is good that you come out with a mock implmentation.

Spying on a non-exported node.js function using jest not working as expected

I am trying to mock a non-exported function via 'jest' and 're-wire'.
Here I am trying to mock 'iAmBatman' (no-pun-intended) but it is not exported.
So I use rewire, which does it job well.
But jest.mock doesn't work as expected.
Am I missing something here or Is there an easy way to achieve the same ?
The error message given by jest is :
Cannot spy the property because it is not a function; undefined given instead
service.js
function iAmBatman() {
return "Its not who I am underneath";
}
function makeACall() {
service.someServiceCall(req => {
iAmBatman();
});
return "response";
}
module.export = {
makeACall : makeACall;
}
jest.js
const services = require('./service');
const rewire = require('rewire');
const app = rewire('./service');
const generateDeepVoice = app.__get__('iAmBatman');
const mockDeepVoice = jest.spyOn(services, generateDeepVoice);
mockDeepVoice.mockImplementation(_ => {
return "But what I do that defines me";
});
describe(`....', () => {
test('....', done => {
services.makeACall(response, () => {
});
});
})

It is not entirely clear what your goal is, but if you look at the documentation of jest.spyOn, you see that it takes a methodName as the second argument, not the method itself:
jest.spyOn(object, methodName)
This explains your error: you didn't give the function name, but the function itself.
In this case, using jest.spyOn(services, 'iAmBatman') wouldn't work, since iAmBatman is not exported, and therefore services.iAmBatman is not defined.
Luckily, you don't need spyOn, as you can simply make a new mock function, and then inject that with rewire's __set__ as follows:
(note that I deleted the undefined service.someServiceCall in your first file, and fixed some typos and redundant imports)
// service.js
function iAmBatman() {
return "Its not who I am underneath";
}
function makeACall() {
return iAmBatman();
}
module.exports = {
makeACall: makeACall
}
// service.test.js
const rewire = require('rewire');
const service = rewire('./service.js');
const mockDeepVoice = jest.fn(() => "But what I do that defines me")
service.__set__('iAmBatman', mockDeepVoice)
describe('service.js', () => {
test('makeACall should call iAmBatman', () => {
service.makeACall();
expect(mockDeepVoice).toHaveBeenCalled();
});
})
Another option would be to restructure your code with iAmBatman in a seperate module, and then mock the module import with Jest. See documentation of jest.mock.