How to write a karma test for a promise - angularjs

Question

I have some code that runs a timer when user is active and broadcasts and event to keep the session alive.
In the controller I have some code to listen for that event and refresh the session.
I want to test this listener
$scope.$on('Keepalive', function () {
//every 45 minutes make a call to refresh the session.
var promise = authService.keepAliveSession();
promise.then(function(userPreferenceData) {
dataTransfer.setUserPref(userPreferenceData);
}, function(error) {
console.log("promise error!!"+error);
});
});
my keepalive service returns a promise which will get resolved after the httpbackend returns.
factory.keepAliveSession = function () {
var deferred = $q.defer();
req=...some stuff...
$http(req)
.success(
function (data, status) {
if ( data.user ) {
// Received data about the logged in user
deferred.resolve(factory.userPreferenceData);
} else {
// User is not authenticated; redirect to login
$window.location = data.redirect;
}
}
).error(function (error) {
// Error in oAuth refresh service
deferred.reject("Error in session keepalive"+ error);
});
return deferred.promise;
}
here is the test
it('Test for keepalive', function() {
console.log('starting for keepalive...');
httpBackend.when('POST', "http://example.com/refreshSession").respond(getMocks().response.oAuthResponseExternal);
spyOn(authServiceMock, "keepAliveSession").and.callThrough();
spyOn(dataTransferMock, "setUserPref").and.callThrough();
rootScope.$broadcast('Keepalive');
expect(authServiceMock.keepAliveSession).toHaveBeenCalled();
rootScope.$digest;
expect(dataTransferMock.setUserPref).toHaveBeenCalled();
});
The first assertion is successful, but the second one (after the digest) fails.
How can I force the promise to be resolved or rejected?
Do I need to somehow mock the $q?

Answer 1

It's hard to say for sure without seeing the mock implementations, how you wire up the module and how you create the controller.
My guess is that the promise that is returned from authServiceMock.keepAliveSession never gets resolved, which would lead to that the success function that dataTransfer.setUserPref lives in never gets executed.
If you for example have a mock that looks like this:
var deferred;
var authServiceMock = {
keepAliveSession: function () {
deferred = q.defer();
return deferred.promise;
}
};
You need to manually in your test either resolve or reject the promise before you trigger the digest cycle, depending on which case you are testing:
expect(authServiceMock.keepAliveSession).toHaveBeenCalled();
deferred.resolve('something');
$rootScope.$digest();
expect(dataTransferMock.setUserPref).toHaveBeenCalled();
Note that you need to execute the $digest function, in your example you just have rootScope.$digest;.
On another note, it seems to me you are mixing testing concerns a bit.
From my point of view, this is what your controller should test:
When the Keepalive event is fired - authService.keepAliveSession should be called
If the promise from authService.keepAliveSession is resolved - dataTransfer.setUserPref should be called and pass the correct data
If the promise from authService.keepAliveSession is rejected - an error message should be logged
The implementation details of the services shouldn't matter (other than that authService.keepAliveSession returns a promise) and you shouldn't need to involve httpBackend in this case.
Setting up fake return data with httpBackend should be used when you test the actual service that uses the $http service.
Below is an alternative way to test this, using spyOn and callFake instead of using mock implementations.
describe('myApp', function() {
var $rootScope;
var $controller;
var authService;
var dataTransfer;
var $log;
var myController;
beforeEach(function() {
module('myApp');
inject(function(_$rootScope_, _$controller_, _authService_, _dataTransfer_, _$q_, _$log_) {
$rootScope = _$rootScope_;
$controller = _$controller_;
authService = _authService_;
dataTransfer = _dataTransfer_;
$q = _$q_;
$log = _$log_;
});
myController = $controller('MyController', {
$scope: $rootScope.$new()
});
});
it('On event "Keepalive" - should call "authService.keepAliveSession"', function() {
spyOn(authService, 'keepAliveSession').and.callFake(function() {
var deferred = $q.defer();
return deferred.promise;
});
$rootScope.$broadcast('Keepalive');
expect(authService.keepAliveSession).toHaveBeenCalled();
});
it('Promise from "authService.keepAliveSession" is resolved - should call "dataTransfer.setUserPref"', function() {
var data = {};
spyOn(authService, 'keepAliveSession').and.callFake(function() {
var deferred = $q.defer();
deferred.resolve(data);
return deferred.promise;
});
spyOn(dataTransfer, 'setUserPref');
$rootScope.$broadcast('Keepalive');
$rootScope.$digest();
expect(dataTransfer.setUserPref).toHaveBeenCalledWith(data);
});
it('Promise from "authService.keepAliveSession" is rejected - should not call "dataTransfer.setUserPref"', function() {
var data = {};
spyOn(authService, 'keepAliveSession').and.callFake(function() {
var deferred = $q.defer();
deferred.reject(data);
return deferred.promise;
});
spyOn(dataTransfer, 'setUserPref');
$rootScope.$broadcast('Keepalive');
$rootScope.$digest();
expect(dataTransfer.setUserPref).not.toHaveBeenCalled();
});
it('Promise from "authService.keepAliveSession" is rejected - should log message', function() {
var error = {};
spyOn(authService, 'keepAliveSession').and.callFake(function() {
var deferred = $q.defer();
deferred.reject(error);
return deferred.promise;
});
spyOn($log, 'log');
$rootScope.$broadcast('Keepalive');
$rootScope.$digest();
expect($log.log).toHaveBeenCalledWith(error);
});
});
Demo: http://plnkr.co/edit/L1uks0skH2N5bAXGoe90?p=preview