AngularJS : How to unit-test a provider

Question

After several hours of searching and experimenting, my mind is blown. A straight-forward and working example of how to unit-test an AngularJS provider is nowhere to be found and I cannot get it to work myself, no matter how hard I try.

In the below example, the service is properly injected and working. The provider is not injected and cannot be configured, because it never arrives in the code-block where configuration should be possible.

Is there anyone that can provide a working 'How to unit-test an AngularJS provider' example ?

angular.module('app',[]);
angular.module('app').service('testBasicService', function () {
    return {
        serviceMethod: function () {
            alert("serviceMethod");
        }
    };
});

angular.module('app').provider('testAdvancedService', function () {
    this.$get = function () {
        this.providerMethod = function () {
            alert("providerMethod");
        }
    }
});


describe("Test", function () {
    beforeEach(module("app"), function (testAdvancedServiceProvider) {
        // code never arrives here
    });

    it("should just work", inject(function (testBasicService,     testAdvancedService) {
        testBasicService.serviceMethod();
        testAdvancedService.providerMethod(); // testAdvancedService is undefined here
    }));
});

Answer 1

I think the reason why testAdvancedService is undefined in your test is because the $get method in the provider doesn't have a return value. If it did return an object, that object would be the testAdvancedService injected in your test.

If you have a function defined in your provider that you want to test, I found that this works:

describe("Test", function () {

    beforeEach(module("app"));

    var provider;
    beforeEach(function () {
        module(function ($provide, testAdvancedServiceProvider) {
            provider = $provide.provider('testAdvancedServiceProvider', testAdvancedServiceProvider);
        });
    });

    it("should just work", inject(function (testBasicService, testAdvancedService) {
        testBasicService.serviceMethod();
        alert(testAdvancedService); // result of the $get function. undefined as it is now.
        provider.providerMethod();
    }));
});