public void TestNormalize()
        {
            var keep = new ImplementationPreferences {
                ID = "id1", UserStability = Stability.Testing
            };
            var superfluous = new ImplementationPreferences {
                ID = "id2"
            };
            var preferences = new FeedPreferences {
                Implementations = { keep, superfluous }
            };

            preferences.Normalize();
            preferences.Implementations.Should().BeEquivalentTo(keep);
        }
        public void TestGetImplementationPreferences()
        {
            var preferences  = new FeedPreferences();
            var preferences1 = preferences["id1"];

            preferences["id1"].Should().BeSameAs(preferences1, because: "Second call with same ID should return same reference");

            var preferences2 = new ImplementationPreferences {
                ID = "id2"
            };

            preferences.Implementations.Add(preferences2);
            preferences["id2"].Should().BeSameAs(preferences2, because: "Call with pre-existing ID should return existing reference");

            preferences.Implementations.Should().BeEquivalentTo(preferences1, preferences2);
        }