public void AddValueOrOverrideTest()
        {
            var dictionary = new Dictionary <int, int> {
                { 1, 2 }
            };

            Dicts.AddValueOrOverride(dictionary, 1, 100);
            Dicts.AddValueOrOverride(dictionary, 2, 200);

            dictionary.Count.ShouldBe(2);
            dictionary[1].ShouldBe(100);
            dictionary[2].ShouldBe(200);

            dictionary.AddValueOrOverride(1, 300);
            dictionary.AddValueOrOverride(3, 400);

            dictionary.Count.ShouldBe(3);
            dictionary[1].ShouldBe(300);
            dictionary[2].ShouldBe(200);
            dictionary[3].ShouldBe(400);
        }