how to check a function in an injected controller?

i'm currently just trying to test if getTodaysHours function on my controller has been called. ultimately the function should get hours from the mock JSON data and pass if parameters match, but i'm stuck on the first part.

vendor.controller

export class VendorController {
    constructor($rootScope, data, event, toastr, moment, _, distanceService, vendorDataService, userDataService, stateManagerService) {
        'ngInject';
        //deps
        this.$rootScope = $rootScope;
        this.toastr = toastr;
        this._ = _;
        this.userDataService = userDataService;
        this.vendorDataService = vendorDataService;
        this.stateManagerService = stateManagerService;
        this.event = event;

        //bootstrap
        data.isDeepLink = true;
        this.data = data;
        this.data.last_update = moment(this.data.updated_at).format('MM/DD/YY h:mm A');
        this.data.distance = distanceService.getDistance(this.data.loc.lng, this.data.loc.lat);
        this.data.todaysHours = this.getTodaysHours();
        this.data.rating_num = Math.floor(data.rating);


        this.hasReviewed = (userDataService.user.reviewed[data._id]) ? true : false;
        this.isGrid = false;
        this.isSearching = false;
        this.hideIntro = true;
        this.menuCollapsed = true;
        this.filterMenuCollapsed = true;

        this.selectedCategory = 'All';
        this.todaysHours = '';
        this.type = '';
        this.searchString = '';

        this.reviewScore = 0;

        this.today = new Date().getDay();

        this.vendorDataService.currentVendor = data;

        //load marker onto map
        $rootScope.$broadcast(event.ui.vendor.pageLoad, data);

        //get menu
        vendorDataService.getVendorMenu(data._id)
            .then((res)=> {
                this.data.menu = res.menu;
                this.menuContainer = this.data.menu;
                this.totalResults = this.getTotalResults();
                this.availableMenuCategories = this.getAvailableMenuCategories();
            })
            .catch(() => {
                this.toastr.error('Whoops, Something went wrong! We were not able to load the menu.',  'Error');
            });
    }

    //get todays hours
    getTodaysHours() {
        let today = this.data.hours[new Date().getDay()];
        return (today.opening_time || '9:00am') + ' - ' + (today.closing_time || '5:00pm');
    }  
}

the first test passes when I mock the JSON data with $provide constant

describe('vendor controller', () => {
    let vm,
        data = {"_id":"56b54f9368e685ca04aa0b87","lat_lon":"33.713018,-117.841101","hours":[{"day_of_the_week":"sun","closing_time":" 7:00pm","opening_time":"11:00am","day_order":0,"id":48880},...];

    beforeEach(angular.mock.module('thcmaps-ui', ($provide) => {
        $provide.constant('data', new data);
      }));

    //first test
    it('should pass', () => {
        expect(data._id).toEqual('56b54f9368e685ca04aa0b87');
    });

    //second test
    it('should call getTodaysHours', () => {
    expect(vm.getTodaysHours()).toHaveBeenCalled();
    });
});

then I tried to inject the controller (not sure if correct syntax):

beforeEach(angular.mock.module('thcmaps-ui', ($provide) => {
    $provide.constant('data', new data);
  }));
beforeEach(inject(($controller) => {
    vm = $controller('VendorController');
    spyOn(vm,'getTodaysHours').and.callThrough();
}));

and it gives me some kind of forEach error. the second test gives me a undefined error when evaluating vm.getTodaysHours().