PDF merge regression checks
Run with the .NET 8 SDK:
dotnet run --project tests/PdfMergeRegression
This console harness links the production merge class and uses the same iText 7.1.13 dependency, without loading WPF. It checks page order, single-file copies, source-path protection, failed merges, replacement, and temporary-file cleanup. It does not change the application's .NET Core 3.1 target.
Also check the WPF application on Windows: after an invalid or inaccessible PDF,
the error must leave the selection and destination intact, without a success
message; after a successful merge, both fields should clear. Check uppercase
.PDF destinations and the single-input case as well.