MigrationEngine contracts. It avoids Tautologies by cleanly substituting IdMappingService without mocking the engine itself. Cross-filter parsing asserts against hard-coded, predefined validation dictionaries (no Logic Mirroring). It successfully addresses @PRE negative cases (e.g. invalid zip paths, missing YAMLs) and rigorously validates @POST file transformations (e.g. in-place UUID substitutions and archive reconstruction)." }