karneyenkadzmitry / calculator_unit-tests

Javascript ( Node.js)

calculator_unit-tests (Javascript ( Node.js))

The application show how testers have to write unit tests.
There is calculator class in [index.js] than we need to coverage unit tests.
It has two methods [add] - for summarising and [multiply] - for multiplication.

The application needs to have the following dependencies:

npm --version 6.4.1
node --version 8.11.4

Deploy

$ npm install

Before start the program is supposed to run the command [npm install].
It downloads needed modules and prepars the programm for start.
There is a list of modules and their versions:

chai: ^4.1.2
chai-spies: ^1.0.0
mocha: ^5.2.0
mochawesome: ^3.0.3
eslint: ^5.6.0
nyc: ^13.1.0

Structure

Folders:

• test - there are all files and folders connected with tests;
• [node_modules] - will be created after [npm install] command. There will be stored all additional modules;
• [reports] - will be created after the first run of [npm test] command. There will be stored all data that are need for report;
• [.nyc-output] - will be created after the first run of [npm test] command. There will be stored all data for [nyc] module.

Files in root:

• index.js - main file in which you can find our Calculator class;
• .eslintignore - all folders and files that should not be indexed by [eslint] are listed here;
• .eslintrc.js - all rulles for [eslint] are placed there;
• .gitignore - all folders and files that should not be indexed by [git] are listed here;
• package.json - includes all data for [npm]
• README.md - readme file with special information about the application and git-syntacs.

Usage

There are some scripts in package.json that helps us.

• 1.[npm run linter] - check style and fix some marks in code. Afret have finished it write errors in console.
• 2.[npm test] - run tests and at the end print results of tests coverage the Calculator class.

Author

Dzmitry_Karneyenka, Republic of Belarus, Minsk

N.B.

beforeEach

Don't put [beforeEach()] in [forEach], because [beforeEach()] multiply on array elements length
that causes running [beforeEach()] block before every it equals array.length times.
It is wrong way. It is better to place [beforeEach()] outside [forEach] but inside [describe] block.

If you use two and more [beforeEach()] - -blocks, they are run in the order of one by one before every it block.

chai-spies

How to make checks with spy?

1. make spy:
   const someSpy = chai.spies.on(object, 'nameOfMethod');
   
   
2. use chai.expect for making assertion:
   chai.expect(someSpy).to.have.been.called.with(data);
   see documentation
   

chai method throw

How to make checks for Errors?

1. Create new function that will include tested method that have to throw an Error with data.
   e.g. const actualResult = () => calculator.add(data);
   
   
2. Send it into check's method. further steps it does itself.It makes listener, runs method and catches an Error.
   e.g. chai.expect(actualResult).to.throw(TypeError);
   see documentation
   

Use spread operator - (...) for:

1. Sending arguments into method from array;
   e.g. obj.functionName(...[a, b, c, d]) spread converts into obj.functionName(a, b, c, d)
   
   
2. making array from arguments in functions;
   e.g. function Name(...arg). If we call the function as obj.Name(a, b, c, d), so arg will be an array [a, b, c, d]
   see documentation