public void TestBefore()
{
var a = new History ();
a.Add (new DateTime (2002, 3, 15));
a.Add (new DateTime (2002, 3, 20));
var b = a.Before (new DateTime (2002, 3, 18));
Assert.False (b.Inverted);
Assert.True (b.Count == 2);
Assert.True (b[0] == new DateTime (2002, 3, 15));
Assert.True (b[1] == new DateTime (2002, 3, 18));
}