How to migrate fabric warehouse data between dev and test workspace in fabric

unfortunately based on my understanding, there is no direct way to restore the data of fabric warehouse from 1 workspace to another.

You would have to use some data transformation or movement tool like either notebooks, datapipelines or dataflow Gen 2.

I am not sure whether the below method would work but you can access the underlying files and folders of fabric warehouse via Azure storage explorere, you can try copying that and pasting into destination warehouse folder >>> need to test this out