public void RemoveTagUsage()
{
var tag = repository.Save(CreateEntry.Tag("rock"));
var tag2 = repository.Save(CreateEntry.Tag("metal"));
var usage = repository.Save(entry.AddTag(tag).Result);
repository.Save(entry.AddTag(tag2).Result);
queries.RemoveTagUsage <SongTagUsage, Song>(usage.Id, repository.OfType <Song>());
Assert.AreEqual(1, entry.Tags.Usages.Count, "Number of tag usages for entry");
Assert.AreEqual(0, tag.UsageCount, "Number of usages for tag");
Assert.IsFalse(entry.Tags.HasTag(tag), "Tag was removed from entry");
}