mocha change global variables

here's my test code

var assert = require('assert');
allCards= require('../poker').allCards

describe('getEnemyCards() should return an array of enemy cards ',function(){

    global.allCards=[["A-C",1],["4-D",1],["8-H",0],["9-S",1],["2-S",1],["7-H",1],["Q-S",1],["K-C",1]]

    it('takes first 2 cards from allCards',function(){  
        assert.deepEqual(getEnemyCards(),  ["A-C","4-D"])
    });

});

And my poker.js code

module.exports.getEnemyCards=getEnemyCards
module.exports.allCards=allCards

var allCards = []
function getEnemyCards(){
//enemy cards check

   var card1=allCards[0][0];
   var card2=allCards[1][0];
   return ([card1,card2]);
}

I tried changing allCards as shown but it remains [] how can i change it? Thanks.