test: cover auth-config helpers and oauth2 cache fix

I added 13 new tests across 5 files, covering the auth-config functions that lacked tests. Categories follow Normal / Boundary / Error where applicable.

`cj/toggle-auth-source-debug` flips state once and back through two toggles. `cj/oauth2-auto--plstore-read-fixed` gets three tests: cache miss reads then caches, cache hit skips `plstore-open` entirely, and the `unwind-protect` runs `plstore-close` even when `plstore-get` signals.

`cj/reset-auth-cache` covers no-prefix (skip `shell-command`), with-prefix success, and with-prefix shell failure (Emacs caches still clear). `cj/kill-gpg-agent` covers shell exit 0 and non-zero. `cj/clear-oauth2-auto-cache` covers bound-with-entries, bound-but-empty, and unbound. The unbound test restores the binding via `unwind-protect` so other tests in the same Emacs session don't void-variable.

I stubbed every boundary via `cl-letf` (`plstore-open`, `plstore-get`, `plstore-close`, `oauth2-auto--compute-id`, `auth-source-forget-all-cached`, `epa-file-clear-cache`, `shell-command`, `message`, `call-process`) and didn't stub any internal helpers.

15 auth-config tests pass together: 2 existing plus 13 new.

1 files changed, 81 insertions, 0 deletions

diff --git a/tests/test-auth-config-reset-auth-cache.el b/tests/test-auth-config-reset-auth-cache.el
new file mode 100644
index 00000000..689ce483
--- /dev/null
+++ b/tests/test-auth-config-reset-auth-cache.el
@@ -0,0 +1,81 @@
+;;; test-auth-config-reset-auth-cache.el --- Tests for cj/reset-auth-cache -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Verifies cache-reset orchestrates auth-source, EPA, and gpg-agent
+;; clears according to the prefix-arg flag.
+
+;;; Code:
+
+(require 'cl-lib)
+(require 'ert)
+(require 'auth-source)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+
+(defun test-auth-config-reset--load ()
+  "Load auth-config with external process calls stubbed."
+  (cl-letf (((symbol-function 'call-process)
+             (lambda (&rest _args) 0)))
+    (load (expand-file-name "modules/auth-config.el" user-emacs-directory)
+          nil t)))
+
+(ert-deftest test-auth-config-reset-auth-cache-normal-no-prefix-skips-shell ()
+  "Normal: no prefix arg clears Emacs caches but does not invoke shell-command."
+  (test-auth-config-reset--load)
+  (let ((auth-clears 0)
+        (epa-clears 0)
+        (shell-calls 0))
+    (cl-letf (((symbol-function 'auth-source-forget-all-cached)
+               (lambda () (cl-incf auth-clears)))
+              ((symbol-function 'epa-file-clear-cache)
+               (lambda () (cl-incf epa-clears)))
+              ((symbol-function 'shell-command)
+               (lambda (&rest _) (cl-incf shell-calls) 0))
+              ((symbol-function 'message) (lambda (&rest _) nil)))
+      (cj/reset-auth-cache nil)
+      (should (= auth-clears 1))
+      (should (= epa-clears 1))
+      (should (zerop shell-calls)))))
+
+(ert-deftest test-auth-config-reset-auth-cache-boundary-with-prefix-shell-success ()
+  "Boundary: with prefix and shell-command returning 0, all three caches clear."
+  (test-auth-config-reset--load)
+  (let ((auth-clears 0)
+        (epa-clears 0)
+        (shell-calls 0)
+        (last-message nil))
+    (cl-letf (((symbol-function 'auth-source-forget-all-cached)
+               (lambda () (cl-incf auth-clears)))
+              ((symbol-function 'epa-file-clear-cache)
+               (lambda () (cl-incf epa-clears)))
+              ((symbol-function 'shell-command)
+               (lambda (&rest _) (cl-incf shell-calls) 0))
+              ((symbol-function 'message)
+               (lambda (fmt &rest _) (setq last-message fmt))))
+      (cj/reset-auth-cache t)
+      (should (= auth-clears 1))
+      (should (= epa-clears 1))
+      (should (= shell-calls 1))
+      (should (string-match-p "Emacs and gpg-agent caches cleared" last-message)))))
+
+(ert-deftest test-auth-config-reset-auth-cache-error-with-prefix-shell-fails ()
+  "Error: with prefix and shell-command non-zero, warning is shown, Emacs caches still cleared."
+  (test-auth-config-reset--load)
+  (let ((auth-clears 0)
+        (epa-clears 0)
+        (last-message nil))
+    (cl-letf (((symbol-function 'auth-source-forget-all-cached)
+               (lambda () (cl-incf auth-clears)))
+              ((symbol-function 'epa-file-clear-cache)
+               (lambda () (cl-incf epa-clears)))
+              ((symbol-function 'shell-command)
+               (lambda (&rest _) 1))
+              ((symbol-function 'message)
+               (lambda (fmt &rest _) (setq last-message fmt))))
+      (cj/reset-auth-cache t)
+      (should (= auth-clears 1))
+      (should (= epa-clears 1))
+      (should (string-match-p "Failed to clear gpg-agent cache" last-message)))))
+
+(provide 'test-auth-config-reset-auth-cache)
+;;; test-auth-config-reset-auth-cache.el ends here