NodeJS - Mocha

1. Error - 오류

'ReferenceError: document is not defined'

Uncaught TypeError: Cannot read property 'value' of null

2. Problem - 문제

NodeJS 에서는 기본적으로 Browser에서 사용되는 DOM에 관한 객체들이 존재하지 않는다.

3. Solved - 해결

uses document in the global scope before you declare the document.

jsdom을 이용하여 DOM을 이용할 수 있다.

Install mocha-jsdom
```
 npm i -D mocha-jsdom
```

Set jsdom() to document in the global scope

 const jsdom = require('mocha-jsdom');
 global.document = jsdom({url: "http://localhost"});

Sample Test

{ROOT_OF_PROJECT}/test/sample-test.spec.js

  var assert = require('assert');
  var jsdom = require('mocha-jsdom');
  global.document = jsdom({url: "http://localhost"});

  describe('Sample Test', function() {      
    it('div element should exists when use createElement('div')', function() {
        var div = document.createElement('div');
      assert.equal(true, div != null);
    });
  });

Run test
```
 mocha
```

4. Reference - 참조

'ReferenceError: document is not defined' error: https://stackoverflow.com/questions/51661741/referenceerror-document-is-not-defined-error
mocha-jsdom - Test frontend libraries in the console using Node.js, mocha and jsdom.: https://www.npmjs.com/package/mocha-jsdom
How to mock window/document with mocha/chai: https://stackoverflow.com/questions/36500723/how-to-mock-window-document-with-mocha-chai
Mess with globals: https://github.com/mochajs/mocha/wiki/Mess-with-globals
Using Chai to test value of HTML element: https://stackoverflow.com/questions/48331488/using-chai-to-test-value-of-html-element
Uncaught TypeError: Cannot read property of null: https://idiallo.com/javascript/uncaught-typeerror-cannot-read-property-of-null