Angular 1.x - Unit Testing a function that returns Promise

var app = angular.module("app");

app.controller("studentController", function($q, studentDataService){
    var vm = this;    
    vm.students = undefined;
    
    activate();
    
    function activate (){
        vm.students = getAllStudents();
    }
    
    function getAllStudents(){
        return studentDataService
        .getAll();
    }
});

it("should get students on activation", function(done){
    // Fixture Setup
    // Exercise Systcode
    var sut = $controller("studentController");
    
    // Verify Outcome
    sut.students.then(function(data){
        expect(data).toBeDefined();    
        done();
    });
    $rootScope.$apply();
    
    // Fixture Teardown
});