public void ClearValueType()
{
var lookup = new MutableLookup<int, int>();
lookup.Add (1, 10);
lookup.Add (1, 12);
lookup.Add (1, 13);
lookup.Add (2, 21);
lookup.Add (2, 22);
lookup.Add (2, 23);
lookup.Clear();
Assert.AreEqual (0, lookup.Count);
Assert.IsFalse (lookup.Contains (1));
Assert.IsFalse (lookup.Contains (2));
}