Understanding injection dependency in app and tests in AngularJS

I have a dependency injection (understanding) problem while testing a directive (AjaxLoader displayed only when there is a pending request).

App declaration :

angular.module('app', [
    'directives.ajaxLoader',
    'services.httpRequestTracker',
    [...]
])

Directive code :

angular.module('directives.ajaxLoader', [])
.directive('ajaxLoader', ['httpRequestTracker',
    function(httpRequestTracker) {
        return {
            templateUrl: 'common/ajaxLoader.tpl.html',
            link: function($scope) { // This function can have more parameters after $scope, $element, $attrs, $controller
                $scope.hasPendingRequests = function() {
                    return httpRequestTracker.hasPendingRequests();
                };
            }
        };
    }
])

Test code :

describe('ajaxLoader', function() {

    beforeEach(function() {
        module('directives.ajaxLoader', 'common/ajaxLoader.tpl.html');
    });

    describe('ajaxLoader directive', function() {});
});

From there, my directive works perfectly well in the browser, but tests fails with an error like :

Error: [$injector:unpr] Unknown provider: httpRequestTrackerProvider <- httpRequestTracker <- ajaxLoaderDirective

Ok, so I need to inject my dependency somewhere. I have two solutions :

• in my directive directly :

angular.module('directives.ajaxLoader', [
     'services.httpRequestTracker'
])

• in my test code directly :

beforeEach(function() {
     module('directives.ajaxLoader', 'common/ajaxLoader.tpl.html', 'services.httpRequestTracker');
});

Both works, but I don't understand which one is the better and why ? And why is it working in my browser from the start and fails in my test ? In both case, all my directives and trackers are injected in my main app declaration

Thanks