Having read that slide, I can only guess that they were fixing up checksums for the pages they modified in known valid, but wrong ways. In other words, if there

Having read that slide, I can only guess that they were fixing up checksums for the pages they modified in known valid, but wrong ways. In other words, if there's a page on disk containing a timestamp and the test wants to bump the timestamp downwards to see what happens later on, then you need to fix that page's checksum otherwise the test will not do what you wanted. Of course that means your mutations have to be "fair" in the sense that your new values should still be valid. Because as you stated, just stomping on blocks and fixing up their checksums seems like a silly test.