Process Test -- How does it know where to go next?

If you select the highest level of the test (red book with question mark) from the Title Explorer new tabs will open in your ribbon named Properties, Behavior and Results. On the Behavior tab is where you can move to user after taking the test and passing or failing (such as a specific page like explained in your example). On the Results tab you'll see an area that states what the lowest passing score must be (in a percentage). I'm attaching images for reference.

The action to look at this criteria is triggered when the user selects the Done button the last page of the test. If the test has been customized (i.e. no Done button) you're looking for the action On ClickundefinedAICC_Lesson_Status to xxxx. Sometimes a developer may even place it on page show of the certificate or last page within the course. xxxx is determined by your LMS provider and a rep should be able to let you know what should be inserted. In most cases it's either pass, Pass, passed, Passed, complete, Complete, completed, or Completed.