How to enable postman function suggestion on Tests tab

How to enable the suggestion function which postman is highlighting in grey background?

This is core functionality, so I would recommend a trip to the Learning Centre.

If you are new to Postman I would recommend the Postman training links which are located under “Resources” in the Learning Centre.

Resources | Postman Learning Center

The “Galaxy API’s 101” course gets you used to sending requests and the GUI.

The “Galaxy Testing and Automation” gets you used to testing your responses and using variables, basic scripting, etc.