--- /dev/null
+#!/usr/bin/env bash
+
+test_description="emacs subject warnings"
+. $(dirname "$0")/test-lib.sh || exit 1
+. $NOTMUCH_SRCDIR/test/test-lib-emacs.sh || exit 1
+
+test_require_emacs
+
+test_begin_subtest "notmuch-test-subject-warning part 1"
+test_emacs_expect_t '(notmuch-test-subject-warning-1)'
+
+test_done
--- /dev/null
+(require 'cl-lib)
+(require 'notmuch-mua)
+
+(defun subject-check-test (&optional fn)
+ "Test `notmuch-mua-subject-check'.
+Optionally, evaluate FN before doing the test.
+
+Return t if the message would be sent, and nil otherwise."
+ (notmuch-mua-mail)
+ (message-goto-subject)
+ (when fn
+ (funcall fn))
+ (prog1
+ (condition-case nil
+ ;; Force `y-or-n-p' to always return `nil', as if the user
+ ;; pressed "n".
+ (cl-letf (((symbol-function 'y-or-n-p)
+ (lambda (&rest args) nil)))
+ (notmuch-mua-subject-check)
+ t)
+ ('error nil))
+ (set-buffer-modified-p nil)
+ (kill-buffer (current-buffer))))
+
+(defvar subject-check-tests
+ '(;; These are okay.
+ (t . (lambda () (insert "something")))
+ ;; These should not be okay.
+ (nil)
+ (nil . (lambda () (insert " ")))
+ (nil . (lambda () (insert " ")))
+ (nil . (lambda () (insert " "))) ; NON-BREAKING SPACE
+ ))
+
+(defun notmuch-test-subject-warning-1 ()
+ (let (output expected)
+ (dolist (test subject-check-tests)
+ (let* ((expect (car test))
+ (body (cdr test))
+ (result (subject-check-test body)))
+ (push expect expected)
+ (push (if (eq result expect)
+ result
+ ;; In the case of a failure, include the test
+ ;; details to make it simpler to debug.
+ (format "%S <-- %S" result body))
+ output)))
+ (notmuch-test-expect-equal output expected)))