old_contents: import { buildCustomStorage } from '../src/Storage'
  import { buildCustomStoragesMap } from '../src/Storage'
  
  const expect = require('chai').expect
  
  describe('Storage', function() {
    let newStorage = buildCustomStorage('fileSystem', ()=>{}, ()=>{}, ()=>{})
    describe('#buildCustomStorage()', function() {
      it('should build the custom storage', function() {
          expect(newStorage).to.have.property('fileSystem')
          expect(newStorage.fileSystem).to.have.property('setValue')
          expect(newStorage.fileSystem.setValue).to.be.a('function')
      });
    });
    describe('#buildCustomStoragesMap()', function() {
      let customStoragesMap = buildCustomStoragesMap('fileSystem', newStorage)
      it('should build the custom storage map', function() {
          expect(customStoragesMap).to.have.property('fileSystem')
          expect(customStoragesMap).to.have.property('cookie')
          expect(customStoragesMap.fileSystem.setValue).to.be.a('function')
      });
    });
  });
  
new_contents: import { buildCustomStorage } from '../src/Storage'
  import { buildCustomStoragesMap } from '../src/Storage'
  import Storage from '../src/Storage'
  
  const expect = require('chai').expect
  
  describe('Storage', function() {
    let newStorage = buildCustomStorage('fileSystem', ()=>{}, ()=>{}, ()=>{})
    let customStoragesMap = buildCustomStoragesMap('fileSystem', newStorage)
    describe('#buildCustomStorage()', function() {
      it('should build the custom storage', function() {
          expect(newStorage).to.have.property('fileSystem')
          expect(newStorage.fileSystem).to.have.property('setValue')
          expect(newStorage.fileSystem.setValue).to.be.a('function')
      });
    });
    describe('#buildCustomStoragesMap()', function() {
      it('should build the custom storage map', function() {
          expect(customStoragesMap).to.have.property('fileSystem')
          expect(customStoragesMap).to.have.property('cookie')
          expect(customStoragesMap.fileSystem.setValue).to.be.a('function')
      });
    });
    describe('#Storage', function(){
      it('should add custom storage to Storage instance', function(){
        let storage = new Storage('fileSystem', newStorage, customStoragesMap)
        expect(storage.STORAGES_MAP).to.have.property('fileSystem')       
      })
    })
  });
  
subject: test storage instance having custom storages map