There are some parts of the code that are essential for reading the existing data file on startup and run rollback-to-stable operation. The files being read can be from a clean or an unclean shutdown, and, might have been written by an older version of WT. Therefore, any changes to such critical parts of the code should be tested to avoid any data loss issues after restart. 

The aim of this ticket is to write a proposal about upgrade/downgrade evergreen tests that can be automatically triggered if these sources files are changed.