testing.zig creates a maildir, config, and notmuch database in a temporary directory and indexes four fixture emails (a two-message thread plus two standalone messages) embedded from src/testdata via @embedFile. This gives unit tests real indexed mail to exercise the bindings against; the corpusDatabase test is the first to round-trip messages through libnotmuch at runtime. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_017i7R7ReKJAHGQpitxGXqrb