When an A/B test is in scheduled state and you would want to cancel it. On clicking "Unapprove Program", an error message shows up saying 'Cannot unapprove program -<program name> - is in use'.
Within the program, go to the trigger campaign which references these assets in their smart list, for example 1. 'Program_1.Email_Asset_1' used in 'Open Emails' trigger step in smart list 2. 'Program_1.Email_Asset_1' used in 'Clicks Link in Email' trigger step in smart list
Remove asset references above within the smart list of the campaign, navigate to program and click "Unapprove Program".
This is due to the program asset being used in trigger campaigns within the program.