This is my version of the solution.
var tomorrow = DateTime.Now.Date.AddDays(1);
var today = DateTime.Now.Date;
var ts = from t in Tests
where t.postdate >= today && t.postdate < tomorrow
group t by t.Name into newt
select new { Name = newt.Key, Count = newt.Count() };
foreach ( var t in ts) {
Console.WriteLine("{0} {1}",t.Count, t.Name);
}
It finds the Test entries that were posted today and counts after grouping by name.