public void Items_ReturnsKeyValuePairForEveryItemInTheMultiValueDictionary() { var source = new[] { new KeyValuePair <string, string>("A", "A"), new KeyValuePair <string, string>("A", "B"), new KeyValuePair <string, string>("A", "C"), new KeyValuePair <string, string>("B", "A"), new KeyValuePair <string, string>("B", "B"), new KeyValuePair <string, string>("C", "A") }; foreach (var kvp in source) { _target.Add(kvp.Key, kvp.Value); } var result = _target.Items(); Assert.All(result, itm => source.Contains(itm)); Assert.All(source, itm => result.Contains(itm)); }