public void Covers()
{
var cr = new CellRange(2, 4, 6, Direction.Horizontal);
Assert.That(cr.Covers(1, 4), Is.False);
Assert.That(cr.Covers(2, 4), Is.True);
Assert.That(cr.Covers(7, 4), Is.True);
Assert.That(cr.Covers(8, 4), Is.False);
Assert.That(cr.Covers(5, 5), Is.False);
}