Error: getItem() method does not exist (Angular, mocking LocalStorage)

I grabbed a snippet of code to mock local storage, however, when I ran the test, it threw this error. As it says, it can't find the getItem method, but I explicitly declared the method outside the beforeEach block. I don't know what's throwing this error - would appreciate tips and suggestions!

Here are my files:

mainCtrl.spec.js

describe('Controller: MainCtrl', function () {
  var store = {};
  var ls = function() {
    return JSON.parse(store.storage);
  };
  var localStorage = {}; 

  var getItem = function(key) {
    return store[key];
  }

  var setItem = function(key, value) {
    store[key] = value;
  }

  beforeEach(function() {
        // setUp.
        module('mytodoApp');

        // LocalStorage mock.
        spyOn(localStorage, 'getItem').andCallFake(getItem); <-- throwing the error
        Object.defineProperty(sessionStorage, "setItem", { writable: true });
        spyOn(localStorage, 'setItem').andCallFake(setItem);
    });

  afterEach(function() {
    store = {};
  });

  var MainCtrl,
    scope;

  // Initialize the controller and a mock scope
  beforeEach(inject(function ($controller, $rootScope) {
    scope = $rootScope.$new();
    MainCtrl = $controller('MainCtrl', {
      $scope: scope
    });
  }));

  it('should have no items to start with', function() {
    // expect(scope.todos.length).toBe(0);
    expect(Object.keys(store).length).toBe(0);
  });
});

mainCtrl.js

angular.module('mytodoApp')
  .controller('MainCtrl', function ($scope, localStorageService) {
    //  breaks on repeat or blank input
    function addTodoFn() {
        $scope.todos.push($scope.todo); 
        $scope.todo = '';   
    }

    function removeTodoFn(index) {
        $scope.todos.splice(index, 1);
    }

    function watchFn() {
      localStorageService.set('todos', $scope.todos);
    }

    //////////

    var todosInStore = localStorageService.get('todos');
    $scope.todos = todosInStore || [];
    $scope.$watch('todos', watchFn, true);
    $scope.addTodo = addTodoFn;
    $scope.removeTodo = removeTodoFn;
  });