When we deploy change sets that contain Apex classes such as controllers, we'll always deploy using default unit testing thus running all test classes. In my mind, this is best practise to ensure the change set and emulation of it running touches everything, and everything is validated.
However, when the change set only contains unit tests, is it bad practice to only run those unit tests to speed up their deployment given they're ran privately?
I haven't encountered nor read of any problems this could cause, but I'm curious.
Is it bad practice when deploying only unit tests to only run those unit tests during deployment?