public void TestNextLowerItem()
{
var alist = new SparseAList <int>(_maxLeafSize, _maxInnerSize);
int?i;
for (i = 0; i < 100; i++)
{
alist.Add(i.Value);
alist.InsertSpace(alist.Count, 1000);
}
i = int.MaxValue;
Assert.AreEqual(alist.NextLowerItem(ref i), 99);
Assert.AreEqual(i.Value, 99099);
i = 99100;
Assert.AreEqual(alist.NextLowerItem(ref i), 99);
Assert.AreEqual(i.Value, 99099);
Assert.AreEqual(alist.NextLowerItem(ref i), 98);
Assert.AreEqual(i.Value, 98098);
i = 55555;
Assert.AreEqual(alist.NextLowerItem(ref i), 55);
Assert.AreEqual(i.Value, 55055);
i = 1002;
Assert.AreEqual(alist.NextLowerItem(ref i), 1);
Assert.AreEqual(i.Value, 1001);
Assert.AreEqual(alist.NextLowerItem(ref i), 0);
Assert.AreEqual(i.Value, 0);
i = 1;
Assert.AreEqual(alist.NextLowerItem(ref i), 0);
Assert.AreEqual(i.Value, 0);
Assert.AreEqual(alist.NextLowerItem(ref i), default(int));
Assert.AreEqual(i.HasValue, false);
i = int.MinValue;
Assert.AreEqual(alist.NextLowerItem(ref i), default(int));
Assert.AreEqual(i.HasValue, false);
// Place a value at the edge of integer space
alist.Clear();
alist.InsertSpace(0, int.MaxValue - 1);
alist.Add(777);
i = int.MinValue;
Assert.AreEqual(alist.NextLowerItem(ref i), default(int));
Assert.AreEqual(i.HasValue, false);
i = int.MaxValue;
Assert.AreEqual(alist.NextLowerItem(ref i), default(int));
Assert.AreEqual(i.HasValue, false);
i = null;
Assert.AreEqual(alist.NextLowerItem(ref i), 777);
Assert.AreEqual(i.Value, int.MaxValue);
}