angularjs component unit test $interval function

I am trying to test the following component's controller lookup function:

lookup () {
this.current = this.$interval(() => {
    console.log("this.currentIndex");
    if (this.index == 1) {
        this.currentIndex = this.index;
    }
});

This is how I am trying to test it:

beforeEach(inject(function($rootScope, $componentController, _$httpBackend_, _$interval_) {
$httpBackend = _$httpBackend_;
$interval = _$interval_;
scope = $rootScope.$new();
controller = $componentController('control', {
    $scope : scope
});


it('test',function(done) {

    controller.lookup();

   //TRIED USING $interval.flush(0) but doesn't help

});

The issue is it is never executing that $interval function..ie. never prints that console.log(this.currentIndex) and not even throwing any errors.

Thanks for any help.