public void GetKeysTest()
        {
            var keyList = dict.GetKeys();

            CollectionAssert.AreEqual(new List <object> {
                key1, key2, key3
            }, keyList);
        }
        public void RemoveFirstEmptyList()
        {
            OrderPreservingDictionary <object, int> dictEmpty = new OrderPreservingDictionary <object, int>();

            dictEmpty.RemoveFirst();
            var keyList = dictEmpty.GetKeys();

            CollectionAssert.AreEqual(new List <object> {
            }, keyList);
        }