test: cover pure-logic gaps found by the coverage audit

I ran make coverage and worked the report function by function, separating real gaps from interactive/IO wrappers that aren't unit-test targets. These tests fill the genuine pure-logic holes: predicates, parsers, formatters, transforms, and three modules that had no test file at all.

New files cover car-member (local-repository), show-kill-insert-item (show-kill-ring), the oauth2-auto plstore cache fix (auth-config), the coverage-core project-root fallback, reconcile--dirty-p, and the recurrence-frequency dispatch in calendar-sync. Extended files add the missing branches: coverage-core's merge-base and diff /dev/null handling plus the staged and branch-vs-main scopes, the detect-system-timezone symlink path, user-constants no-op and optional-failure branches, the elfeed playlist branch with HTML-entity decoding, the duplicate-line no-comment-syntax guard, and several calendar-sync edges (exception field overrides, timestamp seconds and TZID fallback, property-line position advancement, parse-ics nil and out-of-range inputs).

Mocks sit at the real boundaries (plstore, url-retrieve, process-file, git) so each function's own logic runs. Dates come from relative helpers. About 65 tests added across 15 files, and the full suite stays green.

1 files changed, 49 insertions, 0 deletions

diff --git a/tests/test-reconcile--dirty-p.el b/tests/test-reconcile--dirty-p.el
new file mode 100644
index 000000000..a4c372b66
--- /dev/null
+++ b/tests/test-reconcile--dirty-p.el
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+;;; test-reconcile--dirty-p.el --- Tests for cj/reconcile--dirty-p -*- lexical-binding: t -*-
+
+;;; Commentary:
+;; Tests for `cj/reconcile--dirty-p' in reconcile-open-repos.el.  It runs
+;; git status --porcelain via `cj/reconcile--git' and reports clean (nil),
+;; dirty (non-nil), or 'status-failed when git itself errors.  The git call
+;; is stubbed at the `cj/reconcile--git' boundary (it returns a plist).
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+(require 'reconcile-open-repos)
+
+(defmacro test-reconcile-dirty--with-git (plist &rest body)
+  "Run BODY with `cj/reconcile--git' stubbed to return PLIST."
+  (declare (indent 1))
+  `(cl-letf (((symbol-function 'cj/reconcile--git)
+              (lambda (&rest _) ,plist)))
+     ,@body))
+
+;;; Normal Cases
+
+(ert-deftest test-reconcile-dirty-p-clean-returns-nil ()
+  "Normal: exit 0 with empty porcelain output means clean (nil)."
+  (test-reconcile-dirty--with-git '(:exit 0 :output "")
+    (should-not (cj/reconcile--dirty-p "/repo"))))
+
+(ert-deftest test-reconcile-dirty-p-dirty-returns-non-nil ()
+  "Normal: exit 0 with porcelain content means dirty (non-nil)."
+  (test-reconcile-dirty--with-git '(:exit 0 :output " M file.el\n")
+    (should (cj/reconcile--dirty-p "/repo"))))
+
+;;; Boundary Cases
+
+(ert-deftest test-reconcile-dirty-p-whitespace-only-is-clean ()
+  "Boundary: whitespace-only output trims to empty and counts as clean."
+  (test-reconcile-dirty--with-git '(:exit 0 :output "   \n")
+    (should-not (cj/reconcile--dirty-p "/repo"))))
+
+;;; Error Cases
+
+(ert-deftest test-reconcile-dirty-p-git-failure-returns-status-failed ()
+  "Error: a non-zero git exit returns the symbol 'status-failed."
+  (test-reconcile-dirty--with-git '(:exit 128 :output "fatal: not a repo")
+    (should (eq (cj/reconcile--dirty-p "/repo") 'status-failed))))
+
+(provide 'test-reconcile--dirty-p)
+;;; test-reconcile--dirty-p.el ends here