The test should be extended with other scenarios as described in WT-12014 by sue.loverso@mongodb.com:

One extension to the test from WT-11820 would be in generate_data:

• split the populate to insert the first 50%, checkpoint, take the full backup (and/or start incremental).
• insert the latter 50%, checkpoint, (this will generate the bitmap showing changes in the back half of the table)
• remove the 50%
• ...compact...

Since the bitmap should never turn off a modified bit once it is set, either one of two things should happen during the next incremental backup. We should understand what WT does:

1. WT returns a bit that is beyond the new/compacted end-of-file. The should be okay as lseek should succeed and read should return 0 bytes. I think this is the likely situation.
2. WT detects this internally and returns a copy the whole file or indicates the cursor is done.