public void SendBeaconRequestDoesNotAppendIfAdditionalQueryParametersAreNull() { // given string capturedUrl = null; spyClient.DoPostRequest(Arg.Do <string>(u => capturedUrl = u), Arg.Any <string>(), Arg.Any <byte[]>()) .Returns(CreateSuccessHttpResponse()); // when spyClient.SendBeaconRequest(null, null, null); // then var expectedUrl = InitializeBaseUrl(); Assert.That(capturedUrl, Is.EqualTo(expectedUrl.ToString())); }