I can design a solid set of tests now and catch most of what goes wrong. But the weird edge cases and the failures that only show up when two systems talk to each other still slip right past me. Then they blow up in production, and I'm left wondering how I didn't think of that.
More people experience this than they realize.
You can design most tests but edge cases and integration failures still slip past you.
If this sounds familiar, the Library can help you find the bigger picture.