public void AddVisibleTypesByNamespace_Works()
        {
            var configBuilder = new AnalyzerConfigBuilder()
                                .AddVisibleTypesByNamespace(new Namespace("N1"), null)
                                .AddVisibleTypesByNamespace(new Namespace("N2"), new TypeNameSet {
                "T1", "T2"
            });

            configBuilder
            .AddVisibleTypesByNamespace(new Namespace("N2"), new TypeNameSet {
                "T2", "T3"
            })
            .AddVisibleTypesByNamespace(new Namespace("N3"), new TypeNameSet {
                "T4"
            });

            configBuilder.VisibleTypesByNamespace.ShouldBeEquivalentTo(
                new Dictionary <Namespace, TypeNameSet>
            {
                { new Namespace("N1"), null },
                { new Namespace("N2"), new TypeNameSet {
                      "T1", "T2", "T3"
                  } },
                { new Namespace("N3"), new TypeNameSet {
                      "T4"
                  } },
            });
        }