WCET - Worst Case Execution Time, the longest number of CPU cycles required by a service release ever observed and/or theoretically possible given the hardware architecture and algorithm for data processing used in the service.
Wear Leveling - a flash file system method to ensure that maximum capacity and operational longevity is maintained in a flash device which hosts a filesystem - since flash is divided into sectors, with each sector having a maximum expected number of erase/write cycles, this method attempts to keep erase counts for all sectors approximately the same so no one sector wears out early.
White-Box Test - a set of test vectors which drive specific execution paths in a software unit by design so that the software unit test meets specific path, statement, condition, and/or decision coverage criteria - such tests require intimate knowledge of the software unit such as API return codes, error conditions, and I/O ranges.
Write-Back - when a processor updates memory from registers or cache.
Write-Through - when a processor maintains cache/memory coherency by always writing cache and the corresponding memory location on all writes to locations which are cached.