public void TestReadOnly()
{
BTreeDictionary <int, string> data = new BTreeDictionary <int, string>(Comparer, GetSample());
Assert.IsFalse(data.IsReadOnly);
BTreeDictionary <int, string> copy = data.MakeReadOnly();
Assert.IsFalse(ReferenceEquals(data, copy));
Assert.AreEqual(data.Count, copy.Count);
Assert.IsTrue(copy.IsReadOnly);
Assert.IsTrue(ReferenceEquals(copy, copy.MakeReadOnly()));
data = copy.Clone();
Assert.IsFalse(data.IsReadOnly);
Assert.IsFalse(ReferenceEquals(copy, data));
Assert.AreEqual(data.Count, copy.Count);
}