text: 'use strict';
  
  module.exports = (it, expect, collect) => {
    it('should filter collection to items that are an instance of x', () => {
      const Player = function p(name) {
        this.name = name;
      };
  
      const Manager = function p(name) {
        this.name = name;
      };
  
      const Firmino = new Player('Firmino');
      const Salah = new Player('Salah');
      const Klopp = new Manager('Klopp');
  
      const collection = collect([Firmino, Salah, Klopp]);
  
      const filtered = collection.whereInstanceOf(Player);
  
      expect(filtered.all()).to.eql([Firmino, Salah]);
      expect(collection.all()).to.eql([Firmino, Salah, Klopp]);
    });
  };
  