DocumentSessionFactory.cs

public class DocumentSessionFactory : IDisposable
{
    private readonly IDocumentStore documentStore;

    public DocumentSessionFactory()
    {
        documentStore = new EmbeddableDocumentStore { RunInMemory = true };
        documentStore.Initialize();
    }

    public IAsyncDocumentSession CreateSession()
    {
        var db = string.Format("db-{0:N}", Guid.NewGuid());

        // Throws `NullReferenceException` w/ v1.2.2085-unstable from nuget.
        return documentStore.OpenAsyncSession(db);
    }

    public void Dispose()
    {
        if (documentStore != null)
        {
            documentStore.Dispose();
        }
    }
}

FWIW RunInUnreliableYetFastModeThatIsNotSuitableForProduction https://groups.google.com/forum/?fromgroups=#!topic/ravendb/vkiqoiZ6Fsc doesn't seem like it matters at all. RunIN... is for Esent and RunInMemory = Munin