public void Add()
{
Assert.Throws <ArgumentNullException>(() => _dictionary.Add(null, "a null key"));
Assert.Throws <ArgumentException>(() => _dictionary.Add("two", "another second value"));
Assert.Throws <NotSupportedException>((() => _readOnly.Add("bar0", "bar value")));
for (int i = 0; i < 20; i++)
{
string key = String.Format("bar{0}", i);
_dictionary.Add(key, "bar value");
Assert.IsTrue(_dictionary.Contains(new StringStringPair(key, "bar value")));
}
Assert.AreEqual(23, _dictionary.Count);
}