title: how to create a function in PowerPoint VSTO c# Add-in which will change the current slide to the next slide and how can I test it?
body: <p>I am trying to create a VSTO PowerPoint Add-in in c#, which will have a function which changes the current slide onto the next one.
  I am new to VSTO Add-in and don't know how I can implement that and test it.
  I need the function to be called and it has to move to the next slide.
  It also has to find the active slideshow window</p>
  <p>and I also can't understand, how can I test those functions. Should I call them inside ThisAddIn class?...</p>