This was wered by jeff Badger on the Ask the Expert session! Below is the response:
The TestRunner allows you to run automations that are designated as Unit Test automations. To designate an automation as a Unit Test, add an Entry Point to the automation and set the UnitTest property for the Entry Point to True. Toggling this value will allow you to turn off a unit test – this however is only possible at design time.
TestRunner determines the execution order based on the order that the automation entries appear in the project file. This is a little problematic since the Robotics Studio does not show you this information directly. There is a simple way to control this, however. Create your Unit Test automations and name them so that alphabetically they are in the order you would like them to execute. The next step is the trick – create a new folder and move each Unit Test automation into that folder. The act of moving the files will add them to the project file in alphabetic order. If you decide to rename them later on to change the test order you will need to do this simple trick again.