Create an item: test.trap which holds integer values.
Create a calculated item that takes the last value and substracts the previous value:
Create a preprocessing step:
Deliver only one metric to test.trap item.
When the calculated item will execute the expression, the server will crash with a message:
- If there are two metrics in item, then it works.
- If a preprocessing step has been removed, then it works.
Attaching template for faster reproducing: