Selectivity Tests Input Preservation and Uncertain Predicates

Sat, 24 Oct 2026 00:00:00 +0000

The central promise of a reducer is easy to state and surprisingly easy to weaken: the saved input should be smaller, while still satisfying the behavior being investigated. Testing only a successful reduction would miss several ways that promise can go wrong. Selectivity’s verification therefore checks the copies and the evidence around the search, alongside the search itself.

The automated tests cover line reduction, directory file removal and the optional line pass inside directory files. They also check empty input, raw line-ending preservation and files without a final newline. One predicate deliberately overwrites its disposable input. The saved result must still contain the accepted snapshot bytes, and the source must retain its original contents. A permissions test uses a restrictive creation mask to confirm that the copy restores the modeled file permissions explicitly.

Testing on Selectivity.net

Selectivity Tests Input Preservation and Uncertain Predicates