AngularJS testing callbacks to then functions within services - angularjs

Question

I'm looking to write a Jasmine unit test which executes a callback function passed to a then function. This then function is chained to a call to the AngularJS $http service, and it's inside a custom service. Here's the code I'm working with:
app.service('myService', function($rootScope, $http) {
var service = this;
var url = 'http://api.example.com/api/v1/resources';
service.resources = {
current: []
};
service.insertResource = function (resource) {
return $http.post(url, resource).then(function(response){
$rootScope.$broadcast('resources:updated', service.resources.current);
return response;
});
};
});
Here's my attempt to write a test which executes this callback, but to no avail:
describe('resource service', function() {
beforeEach(angular.mock.module('myapp'));
var resourceService;
beforeEach(inject(function(_resourceService_) {
resourceService = _resourceService_;
}));
it('should insert resources', function() {
resourceService.insertResource({});
});
});

Answer 1

There are several approaches you could take:
Use $httpBackend.expectPOST
Use $httpBackend.whenPOST
Move the code in the callback to a named function (not an anonymous one) and write a test for this function. I sometimes take this route b/c I don't want the trouble of writing tests with $httpBackend. I only test the callback function, I don't test that my service is calling the callback. If you can live w/that it's much simpler approach.
Check the documentation for $httpBackend for details. Here's a simple example:
describe('resource service', function() {
beforeEach(angular.mock.module('myapp'));
var resourceService, $httpBackend;
beforeEach(inject(function($injector) {
resourceService = $injector.get('resourceService');
$httpBackend = $injector.get('$httpBackend');
}));
afterEach(function() {
// tests will fail if expected HTTP requests are not made
$httpBackend.verifyNoOutstandingRequests();
// tests will fail if any unexpected HTTP requests are made
$httpBackened.verifyNoOutstandingExpectations();
});
it('should insert resources', function() {
var data: { foo: 1 }; // whatever you are posting
// make an assertion that you expect this POST to happen
// the response can be an object or even a numeric HTTP status code (or both)
$httpBackend.expectPOST('http://api.example.com/api/v1/resources', data).respond({});
// trigger the POST
resourceService.insertResource({});
// This causes $httpBackend to trigger the success/failure callback
// It's how you workaround the asynchronous nature of HTTP requests
// in a synchronous way
$httpBackend.flush();
// now do something to confirm the resource was inserted by the callback
});
});