Javascript – Jasmine Unit Tests for Promise Object

This article represents tips and code samples in relation with how to write unit tests for Promise object when using Jasmine framework. Please feel free to comment/suggest if I missed to mention one or more important points. Also, sorry for the typos.

Following are the key points described later in this article:

• Sample Promise Object
• Unit Tests related with Promise Object

Sample Promise Object

Pay attention to some of the following in the code below:

• Auth module returns a Promise object that returns a User object when resolved or returns an error object in case of error.
• A JSON object is passed to resolve or reject method.
• Save the file as Auth.js within lib folder.

// Promise needs to be imported when executing a module using Node
//
var Promise = require("promise");

function Auth() {
}

Auth.prototype.login = function(user) {
    return new Promise(function(resolve, reject) {
        if(user.username != "" && user.password != "") {
            resolve({username: user.username, age: 40, location: "Hyderabad", firstname: "Ajitesh", lastname: "Shukla"});
        } else {
            if(user.username == ""){
                reject({status:1, message: "Username is invalid"});
            } else {
                reject({status:2, message: "Password is invalid"});
            }
        }
    });
}

module.exports = Auth;

Unit Tests related with Promise Object

Pay attention to some of the following in the code below:

• “done” is passed as argument to each of the “it” or test method.
• Assertion is made within success or error function
• After assertion, “done()” method is called.
• Save the file as AuthSpec.js in spec folder.

describe("Auth", function() {
  var Auth = require('../lib/Auth');
  var auth;

  beforeEach(function() {
    auth = new Auth();
  });

  it("fails with Username as invalid", function(done) {
    var loginPromise = auth.login({username: '', password: 'pass123'});
    loginPromise.then(function(response){
    },function(error){
        expect(error.status).toEqual(1);
        done();
    });
  });

  it("fails with Password as invalid", function(done) {
    var loginPromise = auth.login({username: 'ashukla', password: ''});
    loginPromise.then(function(response){
    },function(error){
        expect(error.status).toEqual(2);
        done();
    });
  });

  it("is successful", function(done) {
    var loginPromise = auth.login({username: 'ashukla', password: 'pass123'});
    loginPromise.then(function(response){
        expect(response.username).toEqual("ashukla");
        expect(response.firstname).toEqual("Ajitesh");
        expect(response.age).toEqual(40);
        done();
    },function(error){
    });
  });
});