public void RemoveExisting()
{
var lookup = new MutableLookup<string, string>();
lookup.Add (null, "blah");
lookup.Add (null, "monkeys");
lookup.Add ("F", "Foo");
lookup.Add ("F", "Foobar");
lookup.Add ("B", "Bar");
Assert.AreEqual (3, lookup.Count);
Assert.IsTrue (lookup.Remove (null, "blah"));
Assert.AreEqual (3, lookup.Count);
Assert.IsTrue (lookup.Remove (null, "monkeys"));
Assert.AreEqual (2, lookup.Count);
Assert.IsTrue (lookup.Remove ("F"));
Assert.AreEqual (1, lookup.Count);
}