How to mock get(id) requests - angularjs

Question

I am building an application prototype and try to mock the REST web-services.
Here is my code:
var mock = angular.module('mock', ['ngMockE2E']);
mock.run(function($httpBackend){
users = [{id:1,name:'John'},{id:2,name:'Jack'}];
$httpBackend.whenGET('/users').respond(users);
$httpBackend.whenGET(new RegExp('\\/users\\/[0-9]+')).respond(users[0]);
}
Everything is ok, my resource User.query() returns all users, and User.get({id:1}) and User.get({id:2}) returns the same user (John).
Now to improve my prototype, I would like to return the appropriate user, matching the good id.
I read in the angular documentation I should be able to replace the RegExp URI by a function. The idea is to extract the id from the url to use it in respond method.
I then tried this:
$httpBackend.whenGET(new function(url){
alert(url);
var regexp = new RegExp('\\/users\\/([0-9]+)');
id = url.match(regexp)[1];
return regexp.test(url);
}).respond(users[id]);
The problem is the url parameter is always undefined. Any idea to achieve my goal?

Answer 1

By using new function(url) your app tries to instantiate a new object from your anonymous function and pass that new object as the first argument of the $httpBackend.whenGET() call.
Of course, at the time of calling whenGET() no URL is provided, thus it is always undefined.
You should pass the function itself (and not an object instanciated using the function). E.g.:
$httpBackend.whenGET(function (url) {
...
}).respond(users[id]);
UPDATE:
After some more digging it turned out that the option to pass a function as the first argument to whenGET was added in version 1.3.0-beta.3. The docs you were reading probably referred to the latest beta version, while you were using an earlier version.
(Note that even versions 1.3.0-beta.1 and 2 did not provide this option.)
Without getting into much detail, responsible for verifying a matching URL is MockHttpExpectation's matchUrl method:
function MockHttpExpectation(method, url, data, headers) {
...
this.matchUrl = function(u) {
if (!url) return true;
if (angular.isFunction(url.test)) return url.test(u);
if (angular.isFunction(url)) return url(u); // <<<<< this line does the trick
return url == u;
};
The line if (angular.isFunction(url)) return url(u); is the one that gives the option to directly pass a function and was added in version 1.3.0-beta.3 (as already mentioned).
But, if you still want to pass a function to a previous AngularJS version, you could "trick" angular into believing you passed a RegExp, by providing an object with a test method.
I.e. replace:
.whenGET(function (url) {...})
with:
.whenGET({test: function (url) {...}})
See, also, this short demo.

Answer 2

I found a solution by using a function in the respond part instead of the when part:
$httpBackend.whenGET(new RegExp('\\/users\\/[0-9]+')).respond(
function(method, url){
var regexp = new RegExp('\\/users\\/([0-9]+)');
var mockId = url.match(regexp)[1];
return [200, users[mockId]];
}
});