//тесты для текущего(твоего) варианта директивы

describe('statsHeight', function() {
    var $compile,
        $rootScope,
        $timeout;

    beforeEach(function () {
        angular.mock.module('gby.common');
    });

    beforeEach(inject(function (_$compile_, _$rootScope_, _$timeout_){
        $compile = _$compile_;
        $rootScope = _$rootScope_;
        $timeout = _$timeout_;
    }));

    it('string length less than 4', function() {
        var element,
            fontSize = 93,
            content = '999';
        element = $compile('<dt stats-height="'+fontSize+'" class="\'list_item_description__number\'" ng-bind="\''+content+'\'"></dt>')($rootScope);
        $rootScope.$digest();
        $timeout.flush();
        expect(element.html().length).toBeLessThan(4);
        expect(element.css('font-size')).toEqual(fontSize+'px');
    });

    it('string length greater than 3', function() {
        var element,
            fontSize = 93,
            content = '999569';
        element = $compile('<dt stats-height="'+fontSize+'" class="\'list_item_description__number\'" ng-bind="\''+content+'\'"></dt>')($rootScope);
        $rootScope.$digest();
        $timeout.flush();
        expect(element.html().length).toBeGreaterThan(3);
        expect(element.css('font-size')).toEqual((fontSize-10*(content.length-1))+'px');
    });
    
});

//мой вариант директивы(без отслеживания baseMetrics), тесты

commonModule.directive('statsHeight', function ($timeout) {
    return {
        restrict: 'A',
        link: function (scope, element, attrs) {
            var collection={};

            scope.$watchCollection(
                function() {
                    collection.length = element.text().length;
                    collection.fontSize = parseFloat(attrs.statsHeight);
                    return collection;
                },
                function (newCollection) {
                    var newFontSize = newCollection.length < 4
                        ? newCollection.fontSize
                        : newCollection.fontSize - 10 * (newCollection.length - 1);
                    element.css({
                        "font-size" : newFontSize
                    });
                });
        }
    }
});

//тесты
describe('statsHeight', function() {
    var $compile,
        $rootScope,
        $timeout;

    beforeEach(function () {
        angular.mock.module('gby.common');
    });

    beforeEach(inject(function (_$compile_, _$rootScope_, _$timeout_){
        $compile = _$compile_;
        $rootScope = _$rootScope_;
        $timeout = _$timeout_;
    }));

    it('string length less than 4', function() {
        var element,
            fontSize = 93,
            content = '999';
        element = $compile('<dt stats-height="'+fontSize+'" class="\'list_item_description__number\'" ng-bind="\''+content+'\'"></dt>')($rootScope);
        $rootScope.$digest();
        expect(element.text().length).toBeLessThan(4);
        expect(element.css('font-size')).toEqual(fontSize+'px');
    });

    it('string length greater than 3', function() {
        var element,
            fontSize = 93,
            content = '999569';
        element = $compile('<dt stats-height="'+fontSize+'" class="\'list_item_description__number\'" ng-bind="\''+content+'\'"></dt>')($rootScope);
        $rootScope.$digest();
        expect(element.text().length).toBeGreaterThan(4);
        console.log((fontSize-10*(content.length-1)));
        expect(element.css('font-size')).toEqual((fontSize-10*(content.length-1))+'px');

    });

});