public void TestMakeAuthUri()
        {
            const string ZANAAM    = "za@medmij";
            const string ID        = "5";
            const string SCOPE     = "za~5";
            const string ZAAUTH    = "https://za.example.com/auth";
            const string PGO_REDIR = "https://pgo.example.com/my-endpoint";
            const string PGO_ID    = "pgo.example.com";

            var gegevensdienstMock = new Mock <IGegevensdienst>();

            gegevensdienstMock.Setup(geg => geg.Zorgaanbiedernaam).Returns(ZANAAM);
            gegevensdienstMock.Setup(geg => geg.Id).Returns(ID);
            gegevensdienstMock.Setup(geg => geg.AuthorizationEndpointUri).Returns(new System.Uri(ZAAUTH));

            var url = PGOOAuth.MakeAuthUri(
                gegevensdienst: gegevensdienstMock.Object,
                clientId: PGO_ID,
                redirectUri: PGO_REDIR,
                state: "abc"
                );

            Assert.StartsWith(ZAAUTH, url.ToString());
            Assert.Contains($"client_id={PGO_ID}", url.Query);
            Assert.Contains($"scope={SCOPE}", url.Query);
        }