public void SendNewSessionRequestDoesNotAppendIfAdditionalQueryParametersAreNull() { // given string capturedUrl = null; spyClient.DoGetRequest(Arg.Do <string>(u => capturedUrl = u), Arg.Any <string>()) .Returns(CreateSuccessHttpResponse()); // when spyClient.SendNewSessionRequest(null); // then var expectedUrl = InitializeBaseUrl(); AppendUrlParameter(expectedUrl, "ns", "1"); Assert.That(capturedUrl, Is.EqualTo(expectedUrl.ToString())); }