angularjs - how to properly use toHaveBeenCalled() for unit testing? -

i need write test sets state test see if statemanagerservice has been called. i'm getting error:

undefined not object (evaluating 'vm.statemanagerservice.go')

main.controller.js

export class maincontroller {     constructor($state, statemanagerservice) {         'nginject';         this.$state = $state;          if($state.current.name === 'main') {             statemanagerservice.go('list');         }     }  } 

unit test main.controller.spec.js

describe('controllers', () => {     let vm;      //     beforeeach(inject(($controller, $state, statemanagerservice) => {         vm = $controller('maincontroller');      }));      it('should call statemanagerservice when current name main', ()=> {         vm.$state.current.name = 'main'         console.log(vm.$state.current.name)         expect(vm.statemanagerservice.go()).tohavebeencalled();     }); 

also (slightly off-topic) i'm still confused why this.$state = $state required. if left out, error saying $state undefined.

update: getting errors

error: spyon not find object spy upon go() (line 1887)

typeerror: undefined not object (evaluating 'vm.statemanagerservice.go')

statemanager.service.js

export class statemanagerservice {     constructor($state, $stateparams, platformdetectservice){         'nginject';         //deps         this.$state = $state;         this.$stateparams = $stateparams;         this.ismobile = platformdetectservice.ismobile;          //internal         this.laststatename = null;         this.laststateparams = null;     }      //storage method current state     go (statename, params){         this.laststateparams = this.$stateparams.page;         this.laststate = this.$state.current.name.split('.')[1];            let nextstate = (this.ismobile) ? 'mobile.' + statename : 'map.' + statename;          this.$state.go(nextstate, params)     }      //returns last state or list     goback (){         let laststate = this.laststate || 'list',             page = this.laststateparams || null;          this.go(laststate, {page})     }  } 

you need verify on function pointer, not return value of function.

it should have been

expect(vm.statemanagerservice.go).tohavebeencalled(); 

note absence of () around go