text: 
  const chai = require('chai'), expect = chai.expect;
  chai.use(require('chai-like'));
  chai.use(require('chai-things'));
  
  const ViewModel = require('../../../structure/view-model');
  
  describe('view-model toJson method', function() {
    
    let classModel = null;
    let instance = null;
  
    before(function() {
      
    });
  
    after(function() {
      
    });
  
    beforeEach(function() {
      class User extends ViewModel 
      {
        constructor(params)
        {
          super();
          this.setParams(params);
        }
      }
      
      classModel = User;    
    });
  
    afterEach(async function() {
      
    });
  
    it('should return children class properties when available', async function() {
      instance = new classModel({
        name: 'KokoRaka',
        username: 'kokoraka'
      });
  
      const jsonString = instance.toJson();
  
      expect(jsonString).to.be.an('string');
  
    });
    it('should return empty string json when children has no member properties', async function() {
      instance = new classModel();
  
      const jsonString = instance.toJson();
  
      expect(jsonString).to.be.an('string');
      expect(jsonString).to.be.equal('{}');
  
    });
  
  });