//singletone.js
class Singleton {
	static GetSingleton( fn ) {
		var instance;
		return function () {
			if ( !instance ) {
				instance = new fn( ...arguments );
			}
			return instance;
		};
	}
}

module.exports = Singleton.GetSingleton;

//animal.js
class Animal {
	constructor( name ) {
		this._name = name;
	}
}

module.exports = Animal;
 

//test.js
const assert = require( 'assert' );
const singletone = require( '../src/singletone' );
const animal = require( '../src/animal' );

describe( 'Singletone', () => {
	describe( '#animal', () => {
		it( 'should be same.', () => {

			const singleAnimal = singletone( animal );
			assert.equal( singleAnimal( 'dog' ), singleAnimal( 'cat' ) );

			assert.equal( singleAnimal( 'dog' ), singleAnimal() );

			const singleAnimal1 = singletone( animal );
			assert.notEqual( singleAnimal( 'dog' ), singleAnimal1( 'dog' ) );

		} )
	} )
} )