Why are my karma unit tests failing with "Unexpected request"? - angularjs

Question

My unit tests are all failing with:
Error: Unexpected request: GET views/partials/listings.html`.
I've been reading through this SO question: Jasmine tests AngularJS Directives with templateUrl, but it appears that the discussion resolves this problem when using the ngMockE2E $httpBackend rather than the ngMock $httpBackend. I've tried to use the .passThrough() method that is mentioned in the accepted answer, but I get this error:
TypeError: '$httpBackend.whenGET('views/partials/listings.html').passThrough' is not a function`
It appears that the passThrough() method is only available on the ngMockE2E $httpBackend.
I wrote my test to mimic the phonecatApp XHR test from the AngularJS tutorial. This is the test that I'm working on:
(function() {
'use strict';
describe('Controller: ListingsCtrl', function() {
var $httpBackend, ListingsCtrl, scope;
$httpBackend = false;
ListingsCtrl = false;
scope = {};
beforeEach(module('app'));
beforeEach(inject(function(_$httpBackend_, $controller, $rootScope) {
$httpBackend = _$httpBackend_;
scope = $rootScope.$new();
ListingsCtrl = $controller('ListingsCtrl', {
$scope: scope
});
$httpBackend.expectGET('/api/listings/active').respond([
{
address: '123 Fake St'
}, {
address: '456 Other Ave'
}
]);
}));
afterEach(function() {
$httpBackend.verifyNoOutstandingExpectation();
$httpBackend.verifyNoOutstandingRequest();
});
it('should have the correct default search parameters', function() {
$httpBackend.flush();
expect(scope.beds).toBe('Any');
expect(scope.maxRent).toBe('None');
expect(scope.search.address).toBe('');
expect(scope.search.side).toBe('');
});
it('should have listings after loading them from the API', function() {
expect(scope.listings.length).toBe(0);
$httpBackend.flush();
expect(scope.listings.length).toBeGreaterThan(0);
});
});
}).call(this);
Both of the tests fail in all four browsers that I test (Opera, Safari, Firefox and Chrome) with the same error message.
I was under the impression that unit testing with karma only loaded the controller code, and therefore wouldn't attempt to load any views or templates. Am I mistaken?

Answer 1

OK, I think there is great deal of confusion here, let me untangle this. Before diving into technical details here are some desirable properties of unit tests:
We want our unit-tests to be fast. Blazing fast. The reason is that we want to run unit tests often, very often (you do TDD, right?).
Unit testing setup should be as straightforward as possible. The reason is that we want the whole process to be as easy as possible. Otherwise people will tend to skip testing and we don't want bugs in our code.
Assuming that we want our tests to be easy to set up running fast you should not be serving templates via HTTP while testing directives with templates. Doing so will make the overall setup more complex (you need to setup a WWW server to serve templates, get the paths "right" etc.) and will slow down tests (additional, async HTTP request + network traffic while running tests).
What you should be doing instead is to preload directives' templates into $templateCache. The easiest way of doing this is to use the karma-ng-html2js-preprocessor. This pre-processor can get HTML files, stringify them as JS and put into $templateCache. If you are looking for a complete project setup with this approach, you can find an excellent example here: https://github.com/vojtajina/ng-directive-testing
To sum up: don't mix unit-testing and e2e mocks in your testing setup. This makes it more complex and slower to run. Preload directive templates into $templateCache instead avoiding any interactions with $http altogether.