Firebase App named '[DEFAULT]' already exists (app/duplicate-app) [duplicate]

Hi I am trying to unit test while developing a simple web with AngularJS + Firebase, but I have a problem defining the spec and trying the test runner

myProject/test/spec/main.js :

describe('Controller: MainCtrl', function() {

var MainCtrl, scope

beforeEach(module('MainApp'));

beforeEach(inject(function ($controller, $rootScope) {
    scope = $rootScope.$new();
    MainCtrl = $controller('MainCtrl', {
        $scope: scope
    })
}));

it('should....',function(){
    expect(true).toBe(true)
})
it('should2....',function(){
    expect(false).toBe(false)
})
});

result:

PhantomJS 2.1.1 (Mac OS X 0.0.0) Controller: MainCtrl should.... FAILED
Error: [$injector:modulerr] Failed to instantiate module MainApp due 
to: Firebase: Firebase App named '[DEFAULT]' already exists 
(app/duplicateapp).

However, defining the spec once is not a problem. For example:

it('should....',function(){
   expect(true).toBe(true)
})

I do not know why this is the reason I give a hint to me

Here is the project I am developing.

https://github.com/parkwookyun/firebase-angular-board

if (!firebase.apps.length) {
   firebase.initializeApp({});
}else {
   firebase.app(); // if already initialized, use that one
}

Similar answer here

I had the same issue using firebase, and I realized that I was initializing the firebase twice, example:

function initializeFirebase(){    
 var config = {
    apiKey: "myApiKey",
    authDomain: "myAuthDomain",
    databaseURL: "myDatabaseUrl",
    storageBucket: "myStorageBocket",
    messagingSenderId: "idhere"   
   };   
   //initialize firebase  
   firebase.initializeApp(config);  
}

In my case I was using react, And I was calling initializeFirebase() from two different components, but I've decided to call it from the parent component. And now I'm able to query my database, insert records, remove, etc.

Hope this helps someone