Query Raven by Index in a unit test

DocumentStoreExtensions.cs

    public static class DocumentStoreExtensions
    {
        public static void SaveSessionAction(this IDocumentStore documentStore, Action<IDocumentSession> action)
        {
            using (IDocumentSession session = documentStore.OpenSession())
            {
                action(session);
                session.SaveChanges();
                documentStore.WaitForStaleIndexes();
            }
        }

        public static void WaitForStaleIndexes(this IDocumentStore documentStore)
        {
            while (documentStore.DatabaseCommands.GetStatistics().StaleIndexes.Length != 0)
            {
                Thread.Sleep(50);
            }
        }
    }

TagsCountByStoryIndex.cs

    public class TagsCountByStory : AbstractIndexCreationTask<Story, TagsCountByStory.Result>
    {
        public TagsCountByStory()
        {
            Map = stories => from story in stories
                             from tag in story.Tags
                             select new
                                        {
                                            TagName = tag,
                                            Count = 1
                                        };

            Reduce = tagMaps => from tagMap in tagMaps
                                group tagMap by tagMap.TagName
                                into tagGroup
                                select new
                                           {
                                               TagName = tagGroup.Key,
                                               Count = tagGroup.Sum(x => x.StoryCount)
                                           };
        }

        public override string IndexName
        {
            get { return "Stories/StoryCountByTag"; }
        }

        public class Result
        {
            public string TagName { get; set; }
            public int StoryCount { get; set; }
        }
    }

TestFixture.cs

public WhenLoadingTheTagsPage()
{
    _documentStore = new EmbeddableDocumentStore
    {
        RunInMemory = true,
        Conventions = new DocumentConvention
                        {
                            DefaultQueryingConsistency = ConsistencyOptions.QueryYourWrites
                        }
    };
    _documentStore.Initialize();
    _documentStore.RegisterListener(new PreventStaleQueries());
    IndexCreation.CreateIndexes(typeof(IndexMarker).Assembly, _documentStore);
    _config = new ConfigurationStore(new TypeMapFactory(), MapperRegistry.AllMappers());
    _config.AddProfile<StoryViewModelProfile>();
}

[Test]
public void ShouldReturnAListOfTagsWithStoryCount()
{
    Story normalStory = SampleData.GetSampleStory();
    Story legacyStory = SampleData.GetSampleLegacyStory();

    _documentStore.SaveSessionAction(session =>
                                            {
                                                session.Store(normalStory); //Contains 1 Tag
                                                session.Store(legacyStory); //Contains 1 Tag
                                            });

    using (var session = _documentStore.OpenSession())
    {
        var tagsByStoryCount = session
            .Query<TagsCountByStory.Result, TagsCountByStory>()
            .OrderBy(x => x.TagName);

        Console.WriteLine(tagsByStoryCount.Count()); //Output is zero tags found

        tagsByStoryCount.ShouldNotBeEmpty(); // FAIL: This is empty for some reason
    }
}