To reproduce:

• Create a Herald rule that triggers for Maniphest tasks, with a condition like "[Is newly created?] [is true]".
• Create any Maniphest Task.
• Go to the Herald Test Console.
• Do a test run on your task.

This fatals with an error like "You must setIsNewObject to a boolean first!".

The fix is probably to call setIsNewObject(false) on the Adapter after it is created in HeraldTestConsoleController.

Differential and Pholio also use this field, and may need a similar fix. You can test them by creating similar rules and doing similar test console runs.