0x06-unittests_in_js

0x06. Unittests in JS

UnitTests Back-end JavaScript ES6 NodeJS ExpressJS Mocha

Resources

Read or watch:

• Mocha documentation
• Chai
• Sinon
• Express
• Request
• How to Test NodeJS Apps using Mocha, Chai and SinonJS

Requirements

• All of your code will be executed on Ubuntu 18.04 using Node 12.x.x
• Allowed editors: vi, vim, emacs, Visual Studio Code
• All your files should end with a new line
• A README.md file, at the root of the folder of the project, is mandatory
• Your code should use the js extension
• When running every test with npm run test *.test.js, everything should pass correctly without any warning or error

Tasks

0. Basic test with Mocha and Node assertion library

Install Mocha using npm:

• Set up a scripts in your package.json to quickly run Mocha using npm test
• You have to use assert

Create a new file named 0-calcul.js:

• Create a function named calculateNumber. It should accepts two arguments (number) a and b
• The function should round a and b and return the sum of it

Test cases

• Create a file 0-calcul.test.js that contains test cases of this function
• You can assume a and b are always number
• Tests should be around the “rounded” part

Tips:

• For the sake of the example, this test suite is slightly extreme and probably not needed
• However, remember that your tests should not only verify what a function is supposed to do, but also the edge cases

Requirements:

• You have to use assert
• You should be able to run the test suite using npm test 0-calcul.test.js
• Every test should pass without any warning

Expected output:

> const calculateNumber = require("./0-calcul.js");
> calculateNumber(1, 3)
4
> calculateNumber(1, 3.7)
5
> calculateNumber(1.2, 3.7)
5
> calculateNumber(1.5, 3.7)
6
>

Run test

bob@dylan:~$ npm test 0-calcul.test.js 

> [email protected] test /root
> ./node_modules/mocha/bin/mocha "0-calcul.test.js"

  calculateNumber
    ✓ ...
    ✓ ...
    ✓ ...
    ...

  130 passing (35ms)
bob@dylan:~$

1. Combining descriptions

Create a new file named 1-calcul.js:

• Upgrade the function you created in the previous task (0-calcul.js)
• Add a new argument named type at first argument of the function. type can be SUM, SUBTRACT, or DIVIDE (string)
• When type is SUM, round the two numbers, and add a and b
• When type is SUBTRACT, round the two numbers, and subtract b from a
• When type is DIVIDE, round the two numbers, and divide a with b - if the rounded value of b is equal to 0, return the string Error

Test cases

• Create a file 1-calcul.test.js that contains test cases of this function
• You can assume a and b are always number
• Usage of describe will help you to organize your test cases

Tips:

• For the sake of the example, this test suite is slightly extreme and probably not needed
• However, remember that your tests should not only verify what a function is supposed to do, but also the edge cases

Requirements:

• You have to use assert
• You should be able to run the test suite using npm test 1-calcul.test.js
• Every test should pass without any warning

Expected output:

> const calculateNumber = require("./1-calcul.js");
> calculateNumber('SUM', 1.4, 4.5)
6
> calculateNumber('SUBTRACT', 1.4, 4.5)
-4
> calculateNumber('DIVIDE', 1.4, 4.5)
0.2
> calculateNumber('DIVIDE', 1.4, 0)
'Error'

2. Basic test using Chai assertion library

While using Node assert library is completely valid, a lot of developers prefer to have a behavior driven development style. This type being easier to read and therefore to maintain.

Let’s install Chai with npm:

• Copy the file 1-calcul.js in a new file 2-calcul_chai.js (same content, same behavior)
• Copy the file 1-calcul.test.js in a new file 2-calcul_chai.test.js
• Rewrite the test suite, using expect from Chai

Tips:

• Remember that test coverage is always difficult to maintain. Using an easier style for your tests will help you
• The easier your tests are to read and understand, the more other engineers will be able to fix them when they are modifying your code

Requirements:

• You should be able to run the test suite using npm test 2-calcul_chai.test.js
• Every test should pass without any warning

3. Spies

Spies are a useful wrapper that will execute the wrapped function, and log useful information (e.g. was it called, with what arguments). Sinon is a library allowing you to create spies.

Let’s install Sinon with npm:

• Create a new file named utils.js
• Create a new module named Utils
• Create a property named calculateNumber and paste your previous code in the function
• Export the Utils module

Create a new file named 3-payment.js:

• Create a new function named sendPaymentRequestToApi. The function takes two argument totalAmount, and totalShipping
• The function calls the Utils.calculateNumber function with type SUM, totalAmount as a, totalShipping as b and display in the console the message The total is: <result of the sum>

Create a new file named 3-payment.test.js and add a new suite named sendPaymentRequestToApi:

• By using sinon.spy, make sure the math used for sendPaymentRequestToApi(100, 20) is the same as Utils.calculateNumber('SUM', 100, 20) (validate the usage of the Utils function)

Requirements:

• You should be able to run the test suite using npm test 3-payment.test.js
• Every test should pass without any warning
• You should use a spy to complete this exercise

Tips:

• Remember to always restore a spy after using it in a test, it will prevent you from having weird behaviors
• Spies are really useful and allow you to focus only on what your code is doing and not the downstream APIs or functions
• Remember that integration test is different from unit test. Your unit test should test your code, not the code of a different function

4. Stubs

Stubs are similar to spies. Except that you can provide a different implementation of the function you are wrapping. Sinon can be used as well for stubs.

Create a new file 4-payment.js, and copy the code from 3-payment.js (same content, same behavior)

Create a new file 4-payment.test.js, and copy the code from 3-payment.test.js

• Imagine that calling the function Utils.calculateNumber is actually calling an API or a very expensive method. You don’t necessarily want to do that on every test run
• Stub the function Utils.calculateNumber to always return the same number 10
• Verify that the stub is being called with type = SUM, a = 100, and b = 20
• Add a spy to verify that console.log is logging the correct message The total is: 10

Requirements:

• You should be able to run the test suite using npm test 4-payment.test.js
• Every test should pass without any warning
• You should use a stub to complete this exercise
• Do not forget to restore the spy and the stub

Tips:

• Using stubs allows you to greatly speed up your test. When executing thousands of tests, saving a few seconds is important
• Using stubs allows you to control specific edge case (e.g a function throwing an error or returning a specific result like a number or a timestamp)

5. Hooks

Hooks are useful functions that can be called before execute one or all tests in a suite

Copy the code from 4-payment.js into a new file 5-payment.js: (same content/same behavior)

Create a new file 5-payment.test.js:

Inside the same describe, create 2 tests: * The first test will call sendPaymentRequestToAPI with 100, and 20: * Verify that the console is logging the string The total is: 120 * Verify that the console is only called once * The second test will call sendPaymentRequestToAPI with 10, and 10: * Verify that the console is logging the string The total is: 20 * Verify that the console is only called once

Requirements:

• You should be able to run the test suite using npm test 5-payment.test.js
• Every test should pass without any warning
• You should use only one spy to complete this exercise
• You should use a beforeEach and a afterEach hooks to complete this exercise

6. Async tests with done

Look into how to support async testing, for example when waiting for the answer of an API or from a Promise

Create a new file 6-payment_token.js:

• Create a new function named getPaymentTokenFromAPI
• The function will take an argument called success (boolean)
• When success is true, it should return a resolved promise with the object {data: 'Successful response from the API' }
• Otherwise, the function is doing nothing.

Create a new file 6-payment_token.test.js and write a test suite named getPaymentTokenFromAPI

• How to test the result of getPaymentTokenFromAPI(true)?

Tips:

• You should be extremely careful when working with async testing. Without calling done properly, your test could be always passing even if what you are actually testing is never executed

Requirements:

• You should be able to run the test suite using npm test 6-payment_token.test.js
• Every test should pass without any warning
• You should use the done callback to execute this test

7. Skip

When you have a long list of tests, and you can’t figure out why a test is breaking, avoid commenting out a test, or removing it. Skip it instead, and file a ticket to come back to it as soon as possible

You will be using this file, conveniently named 7-skip.test.js

const { expect } = require('chai');

describe('Testing numbers', () => {
  it('1 is equal to 1', () => {
    expect(1 === 1).to.be.true;
  });

  it('2 is equal to 2', () => {
    expect(2 === 2).to.be.true;
  });

  it('1 is equal to 3', () => {
    expect(1 === 3).to.be.true;
  });

  it('3 is equal to 3', () => {
    expect(3 === 3).to.be.true;
  });

  it('4 is equal to 4', () => {
    expect(4 === 4).to.be.true;
  });

  it('5 is equal to 5', () => {
    expect(5 === 5).to.be.true;
  });

  it('6 is equal to 6', () => {
    expect(6 === 6).to.be.true;
  });

  it('7 is equal to 7', () => {
    expect(7 === 7).to.be.true;
  });
});

Using the file 7-skip.test.js:

• Make the test suite pass without fixing or removing the failing test
• it description must stay the same

Tips:

• Skipping is also very helpful when you only want to execute the test in a particular case (specific environment, or when an API is not behaving correctly)

Requirements:

• You should be able to run the test suite using npm test 7-skip.test.js
• Every test should pass without any warning

8. Basic Integration testing

In a folder 8-api located at the root of the project directory, copy this package.json over.

{
  "name": "8-api",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "./node_modules/mocha/bin/mocha"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "express": "^4.17.1"
  },
  "devDependencies": {
    "chai": "^4.2.0",
    "mocha": "^6.2.2",
    "request": "^2.88.0",
    "sinon": "^7.5.0"
  }
}

Create a new file api.js:

• By using express, create an instance of express called app
• Listen to port 7865 and log API available on localhost port 7865 to the browser console when the express server is started
• For the route GET /, return the message Welcome to the payment system

Create a new file api.test.js:

• Create one suite for the index page:
  • Correct status code?
  • Correct result?
  • Other?

Server

Terminal 1:

bob@dylan:~/8-api$  node api.js
API available on localhost port 7865

Terminal 2:

bob@dylan:~/8-api$  curl http://localhost:7865 ; echo ""
Welcome to the payment system
bob@dylan:~/8-api$  
bob@dylan:~/8-api$ npm test api.test.js

> [email protected] test /root/8-api
> ./node_modules/mocha/bin/mocha "api.test.js"



  Index page
    ✓ ...
    ✓ ...
    ...

  23 passing (256ms)

bob@dylan:~/8-api$

Tips:

• Since this is an integration test, you will need to have your node server running for the test to pass
• You can use the module request

Requirements:

• You should be able to run the test suite using npm test api.test.js
• Every test should pass without any warnings

9. Regex integration testing

In a folder 9-api, reusing the previous project in 8-api (package.json, api.js and api.test.js)

Modify the file api.js:

• Add a new endpoint: GET /cart/:id
• :id must be only a number (validation must be in the route definition)
• When access, the endpoint should return Payment methods for cart :id

Modify the file api.test.js:

• Add a new test suite for the cart page:
  • Correct status code when :id is a number?
  • Correct status code when :id is NOT a number (=> 404)?
  • etc.

Server

Terminal 1:

bob@dylan:~$ node api.js
API available on localhost port 7865

Terminal 2:

bob@dylan:~$ curl http://localhost:7865/cart/12 ; echo ""
Payment methods for cart 12
bob@dylan:~$ 
bob@dylan:~$ curl http://localhost:7865/cart/hello -v
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 7865 (#0)
> GET /cart/hello HTTP/1.1
> Host: localhost:7865
> User-Agent: curl/7.58.0
> Accept: */*
> 
< HTTP/1.1 404 Not Found
< X-Powered-By: Express
< Content-Security-Policy: default-src 'none'
< X-Content-Type-Options: nosniff
< Content-Type: text/html; charset=utf-8
< Content-Length: 149
< Date: Wed, 15 Jul 2020 08:33:44 GMT
< Connection: keep-alive
< 
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Error</title>
</head>
<body>
<pre>Cannot GET /cart/hello</pre>
</body>
</html>
* Connection #0 to host localhost left intact
bob@dylan:~$

Tips:

• You will need to add a small regex in your path to support the usecase

Requirements:

• You should be able to run the test suite using npm test api.test.js
• Every test should pass without any warning

10. Deep equality & Post integration testing

In a folder 10-api, reusing the previous project in 9-api (package.json, api.js and api.test.js)

Modify the file api.js:

• Add an endpoint GET /available_payments that returns an object with the following structure:

{
  payment_methods: {
    credit_cards: true,
    paypal: false
  }
}

• Add an endpoint POST /login that returns the message Welcome :username where :username is the value of the body variable userName.

Modify the file api.test.js:

• Add a test suite for the /login endpoint
• Add a test suite for the /available_payments endpoint

Server

Terminal 1:

bob@dylan:~$ node api.js
API available on localhost port 7865

Terminal 2:

bob@dylan:~$ curl http://localhost:7865/available_payments ; echo ""
{"payment_methods":{"credit_cards":true,"paypal":false}}
bob@dylan:~$ 
bob@dylan:~$ curl -XPOST http://localhost:7865/login -d '{ "userName": "Betty" }' -H 'Content-Type: application/json' ; echo ""
Welcome Betty
bob@dylan:~$

Tips:

• Look at deep equality to compare objects

Requirements:

• You should be able to run the test suite using npm test api.test.js
• Every test should pass without any warning
• Your server should not display any error