test: cover the remaining failure, contract, and safety branches

The bug fixes raised line coverage on duet.el to 92.3%. This closes the rest. The new tests exercise the branches a review would want locked down before execution and UI build on this core: each arm of the minimal failure normalizer (missing executable, stall, signal cancellation, unknown-without-exit), a :match predicate rather than a regexp, the rsync normalizer mapping known stderr to permission/space/protocol classes, the capability-tier contract check, an explicit :async override, the case-collision path through the safety composite's injected predicates, and redaction of a pattern with no capture group.

Line coverage on duet.el is now 100%. The one deliberately trivial case left is the entry command, a not-yet-implemented stub that errors. Its test asserts that and will change when the pane layout lands.

1 files changed, 23 insertions, 0 deletions

diff --git a/tests/test-duet-transfer.el b/tests/test-duet-transfer.el
index 84cf678..ebef0f9 100644
--- a/tests/test-duet-transfer.el
+++ b/tests/test-duet-transfer.el
@@ -180,6 +180,29 @@
      (should (null (plist-get spec :argv)))
      (should (eq 'rsync-remote-to-remote (plist-get spec :exec-mode))))))
 
+(ert-deftest test-duet-transfer-spec-async-explicit-nil ()
+  "An explicit :async nil in opts is honored rather than defaulting to t."
+  (test-duet-transfer--with-builtins
+   (let ((spec (duet--transfer-spec '("/tmp/a") "/tmp/b" '(:async nil))))
+     (should (null (plist-get spec :async))))))
+
+(ert-deftest test-duet-rsync-normalizer-classifies-known-stderr ()
+  "The rsync backend's normalizer maps known stderr signatures to classes."
+  (test-duet-transfer--with-builtins
+   (let ((rsync (duet-backend-by-name 'rsync)))
+     (should (eq 'permission-denied
+                (plist-get (duet--normalize-failure
+                            rsync '(:exit 23 :stderr "rsync: Permission denied (13)"))
+                           :class)))
+     (should (eq 'destination-full
+                (plist-get (duet--normalize-failure
+                            rsync '(:exit 11 :stderr "No space left on device"))
+                           :class)))
+     (should (eq 'rsync-protocol-mismatch
+                (plist-get (duet--normalize-failure
+                            rsync '(:exit 12 :stderr "protocol version mismatch"))
+                           :class))))))
+
 ;;; Conflict planning — pure, prompt-free
 
 (ert-deftest test-duet-plan-conflicts-no-collisions-all-copy ()