You have several possibilities to debug your uSignals and uBundles. In play mode you can raise your them at any time.

uDebug

The udebug window shows you all called usignals.

Image module
Raise in PlayMode

To raise in play mode simple enter the unity play mode and select your uSignal or uBundle. Then select the uSignal or uBundle you want to raise. Then you can simply raise the signal with or without a parameter.

Image module