Tools for Promises Unit Testing

Venkat.R

32.1K views

01 Introduction

02 What are those Tools?

03 Simple Unit Testing

04 Unit Testing with Dependent Files

05 Unit Testing with Async.js

Previous: Simple Unit Testing Next: Unit Testing with Async.js

Promise with dependent Files.

In Real time, Long files used to be split into number of small files as models, libs and services. Here, We will see service File which is included the db helper file where we get the DB data.

Service File

const db = require('./db');
function getResultData(name) {
    let payload;
    if (name) {
        payload = {
            prop1: `value1-${name}`,
            prop2: `value2-${name}`,
        };
    }
    return new Promise((resolve, reject) => {
        db.getData(payload).then((data) => {
            if (data.error) {
                reject(data);
            }
            resolve(data);
        });
    });
}
module.exports = {
    getResultData,
};

DB Helper File

function getData(payload) {
    return new Promise((resolve, reject) => {
        if(!payload) {
            reject({
                error: true,
            });
        }
        setTimeout(() => {
            resolve({
                name1: 'value1',
                name2: 'value2',
            });
        }, 5000);
    });
}
module.exports = {
    getData,
};

Unit Testing

This Unit Testing included Mocha, Chai and Sinon Libraries and included file like Service and DB Helper.

Here, you can notice there is before, beforeEach, after hook were added for method request params and response with Sinon Stubs. It actually helps to proxy the calls of DB Library.

Why we need Sinon?

SinonJS has many good features. Below are few methods and we used for Stubs.

Service File Unit Testing

const mocha = require('mocha');
const expect = require('chai').expect;
const sinon = require('sinon');
const db = require('./db');
const service = require('./service');
describe('service.js', () => {
    let noop, label, payload,  response, dbStub;
    before(() => {
        noop = () => {};
        label = 'emp';
        payload;
        response;
        dbStub;
    });
    beforeEach(() => {
        payload = {
            prop1: `value1-${label}`,
            prop2: `value2-${label}`,
        };
        response = {
            name1: 'value1',
            name2: 'value2',
        };
        dbStub = sinon.stub(db, 'getData').callsFake(() => {
            return Promise.resolve(response);
        });
    });
    afterEach(() => {
        dbStub.restore();
    });
    it('should return error response', () => {
        return service.getResultData().then(noop, (data) => {
            expect(data).to.deep.equal({
                error: true,
            });
        });
    });
    it('should return success response', () => {
        return service.getResultData(label).then((data) => {
            expect(data).to.deep.equal(response);
        });
    });
});

Create your playground on Tech.io

This playground was created on Tech.io, our hands-on, knowledge-sharing platform for developers.

Go to tech.io

ABOUT US CAREERS PRIVACY FAQ BLOG

The #1 tech hiring platform

SCREENING INTERVIEWING

Promise with dependent Files.

Unit Testing

Why we need Sinon?

JavaScript promises, mastering the asynchronous

JavaScript, async and await keywords

Common patterns with Solid

ES6 Tutorials : SPREAD Operator with Fun