VST3PluginTestHost force mono

I wish to test my plugin with mono bus. How can I force VST3PluginTestHost to request 1 mono channel.
I set both AudioPorts Outputs to “Wave 1” but it still seems to request SpeakerArrangement stereo (0x3)

try in your processor:

tresult PLUGIN_API MyProcessor::initialize (FUnknown* context)
    addAudioInput (STR16 ("AudioInput"), SpeakerArr::kMono);
    addAudioOutput (STR16 ("AudioOutput"), SpeakerArr::kMono);
tresult PLUGIN_API MyProcessor::setBusArrangements (SpeakerArrangement* inputs, int32 numIns, SpeakerArrangement* outputs, int32 numOuts)
  // we only support one in and output bus and these busses must have the same number of channels and should be Mono
if (numIns == 1 && numOuts == 1 && inputs[0] == outputs[0] && input[0] == SpeakerArr::kMono)
	return AudioEffect::setBusArrangements (inputs, numIns, outputs, numOuts);
  return kResultFalse;