New macro 'ert-with-message-capture'

* lisp/emacs-lisp/ert-x.el (ert-with-message-capture): New macro.
(Bug#25158)

* test/lisp/autorevert-tests.el (auto-revert--wait-for-revert)
(auto-revert-test00-auto-revert-mode)
(auto-revert-test01-auto-revert-several-files)
(auto-revert-test02-auto-revert-deleted-file)
(auto-revert-test03-auto-revert-tail-mode)
(auto-revert-test04-auto-revert-mode-dired):
* test/lisp/filenotify-tests.el (file-notify-test03-autorevert): Use
ert-with-message-capture.

3 files changed, 125 insertions, 121 deletions

diff --git a/lisp/emacs-lisp/ert-x.el b/lisp/emacs-lisp/ert-x.el
index 8530253d5b4..4cf9d9609e9 100644
--- a/lisp/emacs-lisp/ert-x.el
+++ b/lisp/emacs-lisp/ert-x.el
@@ -285,6 +285,30 @@ BUFFER defaults to current buffer.  Does not modify BUFFER."
             (kill-buffer clone)))))))
 
 
+(defmacro ert-with-message-capture (var &rest body)
+  "Execute BODY while collecting anything written with `message' in VAR.
+
+Capture all messages produced by `message' when it is called from
+Lisp, and concatenate them separated by newlines into one string.
+
+This is useful for separating the issuance of messages by the
+code under test from the behavior of the *Messages* buffer."
+  (declare (debug (symbolp body))
+           (indent 1))
+  (let ((g-advice (cl-gensym)))
+    `(let* ((,var "")
+            (,g-advice (lambda (func &rest args)
+                         (if (or (null args) (equal (car args) ""))
+                             (apply func args)
+                           (let ((msg (apply #'format-message args)))
+                             (setq ,var (concat ,var msg "\n"))
+                             (funcall func "%s" msg))))))
+       (advice-add 'message :around ,g-advice)
+       (unwind-protect
+           (progn ,@body)
+         (advice-remove 'message ,g-advice)))))
+
+
 (provide 'ert-x)
 
 ;;; ert-x.el ends here
diff --git a/test/lisp/autorevert-tests.el b/test/lisp/autorevert-tests.el
index aea855ae02f..c082ba95639 100644
--- a/test/lisp/autorevert-tests.el
+++ b/test/lisp/autorevert-tests.el
@@ -24,24 +24,29 @@
 ;;; Code:
 
 (require 'ert)
+(require 'ert-x)
 (require 'autorevert)
 (setq auto-revert-notify-exclude-dir-regexp "nothing-to-be-excluded"
       auto-revert-stop-on-user-input nil)
 
 (defconst auto-revert--timeout 10
-  "Time to wait until a message appears in the *Messages* buffer.")
+  "Time to wait for a message.")
+
+(defvar auto-revert--messages nil
+  "Used to collect messages issued during a section of a test.")
 
 (defun auto-revert--wait-for-revert (buffer)
-  "Wait until the *Messages* buffer reports reversion of BUFFER."
+  "Wait until a message reports reversion of BUFFER.
+This expects `auto-revert--messages' to be bound by
+`ert-with-message-capture' before calling."
   (with-timeout (auto-revert--timeout nil)
-    (with-current-buffer "*Messages*"
-      (while
-          (null (string-match
-                 (format-message "Reverting buffer `%s'." (buffer-name buffer))
-                 (buffer-string)))
-        (if (with-current-buffer buffer auto-revert-use-notify)
-            (read-event nil nil 0.1)
-          (sleep-for 0.1))))))
+    (while
+        (null (string-match
+               (format-message "Reverting buffer `%s'." (buffer-name buffer))
+               auto-revert--messages))
+      (if (with-current-buffer buffer auto-revert-use-notify)
+          (read-event nil nil 0.1)
+        (sleep-for 0.1)))))
 
 (ert-deftest auto-revert-test00-auto-revert-mode ()
   "Check autorevert for a file."
@@ -51,41 +56,38 @@
         buf)
     (unwind-protect
         (progn
-          (with-current-buffer (get-buffer-create "*Messages*")
-            (narrow-to-region (point-max) (point-max)))
-          (write-region "any text" nil tmpfile nil 'no-message)
+          (write-region "any text" nil tmpfile nil 'no-message)
           (setq buf (find-file-noselect tmpfile))
-          (with-current-buffer buf
-            (should (string-equal (buffer-string) "any text"))
-            ;; `buffer-stale--default-function' checks for
-            ;; `verify-visited-file-modtime'.  We must ensure that it
-            ;; returns nil.
-            (sleep-for 1)
-            (auto-revert-mode 1)
-            (should auto-revert-mode)
+          (with-current-buffer buf
+            (ert-with-message-capture auto-revert--messages
+              (should (string-equal (buffer-string) "any text"))
+              ;; `buffer-stale--default-function' checks for
+              ;; `verify-visited-file-modtime'.  We must ensure that it
+              ;; returns nil.
+              (sleep-for 1)
+              (auto-revert-mode 1)
+              (should auto-revert-mode)
 
-            ;; Modify file.  We wait for a second, in order to have
-            ;; another timestamp.
-            (sleep-for 1)
-            (write-region "another text" nil tmpfile nil 'no-message)
+              ;; Modify file.  We wait for a second, in order to have
+              ;; another timestamp.
+              (sleep-for 1)
+              (write-region "another text" nil tmpfile nil 'no-message)
 
-            ;; Check, that the buffer has been reverted.
-            (auto-revert--wait-for-revert buf)
+              ;; Check, that the buffer has been reverted.
+              (auto-revert--wait-for-revert buf))
             (should (string-match "another text" (buffer-string)))
 
             ;; When the buffer is modified, it shall not be reverted.
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (narrow-to-region (point-max) (point-max)))
-            (set-buffer-modified-p t)
-            (sleep-for 1)
-            (write-region "any text" nil tmpfile nil 'no-message)
+            (ert-with-message-capture auto-revert--messages
+              (set-buffer-modified-p t)
+              (sleep-for 1)
+              (write-region "any text" nil tmpfile nil 'no-message)
 
-            ;; Check, that the buffer hasn't been reverted.
-            (auto-revert--wait-for-revert buf)
+              ;; Check, that the buffer hasn't been reverted.
+              (auto-revert--wait-for-revert buf))
             (should-not (string-match "any text" (buffer-string)))))
 
       ;; Exit.
-      (with-current-buffer "*Messages*" (widen))
       (ignore-errors
         (with-current-buffer buf (set-buffer-modified-p nil))
         (kill-buffer buf))
@@ -106,13 +108,11 @@
           (make-temp-file (expand-file-name "auto-revert-test" tmpdir1)))
          buf1 buf2)
     (unwind-protect
-        (progn
-          (with-current-buffer (get-buffer-create "*Messages*")
-            (narrow-to-region (point-max) (point-max)))
-          (write-region "any text" nil tmpfile1 nil 'no-message)
-          (setq buf1 (find-file-noselect tmpfile1))
-          (write-region "any text" nil tmpfile2 nil 'no-message)
-          (setq buf2 (find-file-noselect tmpfile2))
+        (ert-with-message-capture auto-revert--messages
+          (write-region "any text" nil tmpfile1 nil 'no-message)
+          (setq buf1 (find-file-noselect tmpfile1))
+          (write-region "any text" nil tmpfile2 nil 'no-message)
+          (setq buf2 (find-file-noselect tmpfile2))
 
           (dolist (buf (list buf1 buf2))
             (with-current-buffer buf
@@ -148,7 +148,6 @@
               (should (string-match "another text" (buffer-string))))))
 
       ;; Exit.
-      (with-current-buffer "*Messages*" (widen))
       (ignore-errors
         (dolist (buf (list buf1 buf2))
           (with-current-buffer buf (set-buffer-modified-p nil))
@@ -165,8 +164,6 @@
         buf)
     (unwind-protect
         (progn
-          (with-current-buffer (get-buffer-create "*Messages*")
-            (narrow-to-region (point-max) (point-max)))
           (write-region "any text" nil tmpfile nil 'no-message)
           (setq buf (find-file-noselect tmpfile))
           (with-current-buffer buf
@@ -184,42 +181,36 @@
              'before-revert-hook
              (lambda () (delete-file buffer-file-name))
              nil t)
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (narrow-to-region (point-max) (point-max)))
-            (sleep-for 1)
-            (write-region "another text" nil tmpfile nil 'no-message)
 
-            ;; Check, that the buffer hasn't been reverted.  File
-            ;; notification should be disabled, falling back to
-            ;; polling.
-            (auto-revert--wait-for-revert buf)
+            (ert-with-message-capture auto-revert--messages
+              (sleep-for 1)
+              (write-region "another text" nil tmpfile nil 'no-message)
+              (auto-revert--wait-for-revert buf))
+            ;; Check, that the buffer hasn't been reverted.  File
+            ;; notification should be disabled, falling back to
+            ;; polling.
             (should (string-match "any text" (buffer-string)))
             (should-not auto-revert-use-notify)
 
             ;; Once the file has been recreated, the buffer shall be
             ;; reverted.
             (kill-local-variable 'before-revert-hook)
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (narrow-to-region (point-max) (point-max)))
-            (sleep-for 1)
-            (write-region "another text" nil tmpfile nil 'no-message)
-
-            ;; Check, that the buffer has been reverted.
-            (auto-revert--wait-for-revert buf)
+            (ert-with-message-capture auto-revert--messages
+              (sleep-for 1)
+              (write-region "another text" nil tmpfile nil 'no-message)
+              (auto-revert--wait-for-revert buf))
+            ;; Check, that the buffer has been reverted.
             (should (string-match "another text" (buffer-string)))
 
             ;; An empty file shall still be reverted.
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (narrow-to-region (point-max) (point-max)))
-            (sleep-for 1)
-            (write-region "" nil tmpfile nil 'no-message)
-
-            ;; Check, that the buffer has been reverted.
-            (auto-revert--wait-for-revert buf)
+            (ert-with-message-capture auto-revert--messages
+              (sleep-for 1)
+              (write-region "" nil tmpfile nil 'no-message)
+              (auto-revert--wait-for-revert buf))
+            ;; Check, that the buffer has been reverted.
             (should (string-equal "" (buffer-string)))))
 
       ;; Exit.
-      (with-current-buffer "*Messages*" (widen))
       (ignore-errors
         (with-current-buffer buf (set-buffer-modified-p nil))
         (kill-buffer buf))
@@ -232,9 +223,7 @@
   (let ((tmpfile (make-temp-file "auto-revert-test"))
         buf)
     (unwind-protect
-        (progn
-          (with-current-buffer (get-buffer-create "*Messages*")
-            (narrow-to-region (point-max) (point-max)))
+        (ert-with-message-capture auto-revert--messages
           (write-region "any text" nil tmpfile nil 'no-message)
           (setq buf (find-file-noselect tmpfile))
           (with-current-buffer buf
@@ -259,7 +248,6 @@
              (string-match "modified text\nanother text" (buffer-string)))))
 
       ;; Exit.
-      (with-current-buffer "*Messages*" (widen))
       (ignore-errors (kill-buffer buf))
       (ignore-errors (delete-file tmpfile)))))
 
@@ -283,33 +271,29 @@
             (should
              (string-match name (substring-no-properties (buffer-string))))
 
-            ;; Delete file.  We wait for a second, in order to have
-            ;; another timestamp.
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (narrow-to-region (point-max) (point-max)))
-            (sleep-for 1)
-            (delete-file tmpfile)
-
-            ;; Check, that the buffer has been reverted.
-            (auto-revert--wait-for-revert buf)
+            (ert-with-message-capture auto-revert--messages
+              ;; Delete file.  We wait for a second, in order to have
+              ;; another timestamp.
+              (sleep-for 1)
+              (delete-file tmpfile)
+              (auto-revert--wait-for-revert buf))
+            ;; Check, that the buffer has been reverted.
             (should-not
              (string-match name (substring-no-properties (buffer-string))))
 
-            ;; Make dired buffer modified.  Check, that the buffer has
-            ;; been still reverted.
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (narrow-to-region (point-max) (point-max)))
-            (set-buffer-modified-p t)
-            (sleep-for 1)
-            (write-region "any text" nil tmpfile nil 'no-message)
+            (ert-with-message-capture auto-revert--messages
+              ;; Make dired buffer modified.  Check, that the buffer has
+              ;; been still reverted.
+              (set-buffer-modified-p t)
+              (sleep-for 1)
+              (write-region "any text" nil tmpfile nil 'no-message)
 
-            ;; Check, that the buffer has been reverted.
-            (auto-revert--wait-for-revert buf)
+              (auto-revert--wait-for-revert buf))
+            ;; Check, that the buffer has been reverted.
             (should
              (string-match name (substring-no-properties (buffer-string))))))
 
       ;; Exit.
-      (with-current-buffer "*Messages*" (widen))
       (ignore-errors
         (with-current-buffer buf (set-buffer-modified-p nil))
         (kill-buffer buf))
diff --git a/test/lisp/filenotify-tests.el b/test/lisp/filenotify-tests.el
index db7f55e8fc5..27434bcef20 100644
--- a/test/lisp/filenotify-tests.el
+++ b/test/lisp/filenotify-tests.el
@@ -36,6 +36,7 @@
 ;;; Code:
 
 (require 'ert)
+(require 'ert-x)
 (require 'filenotify)
 (require 'tramp)
 
@@ -703,21 +704,19 @@ delivered."
             (should auto-revert-notify-watch-descriptor)
 
             ;; Modify file.  We wait for a second, in order to have
-            ;; another timestamp.
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (narrow-to-region (point-max) (point-max)))
-            (sleep-for 1)
-            (write-region
-             "another text" nil file-notify--test-tmpfile nil 'no-message)
-
-            ;; Check, that the buffer has been reverted.
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (file-notify--wait-for-events
-               timeout
-               (string-match
+            ;; another timestamp.
+            (ert-with-message-capture captured-messages
+              (sleep-for 1)
+              (write-region
+               "another text" nil file-notify--test-tmpfile nil 'no-message)
+
+              ;; Check, that the buffer has been reverted.
+              (file-notify--wait-for-events
+               timeout
+               (string-match
                 (format-message "Reverting buffer `%s'." (buffer-name buf))
-                (buffer-string))))
-            (should (string-match "another text" (buffer-string)))
+                captured-messages))
+              (should (string-match "another text" (buffer-string))))
 
             ;; Stop file notification.  Autorevert shall still work via polling.
             (file-notify-rm-watch auto-revert-notify-watch-descriptor)
@@ -728,27 +727,24 @@ delivered."
 
             ;; Modify file.  We wait for two seconds, in order to
             ;; have another timestamp.  One second seems to be too
-            ;; short.
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (narrow-to-region (point-max) (point-max)))
-            (sleep-for 2)
-            (write-region
-             "foo bla" nil file-notify--test-tmpfile nil 'no-message)
-
-            ;; Check, that the buffer has been reverted.
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (file-notify--wait-for-events
-               timeout
-               (string-match
-                (format-message "Reverting buffer `%s'." (buffer-name buf))
-                (buffer-string))))
-            (should (string-match "foo bla" (buffer-string))))
+            ;; short.
+            (ert-with-message-capture captured-messages
+              (sleep-for 2)
+              (write-region
+               "foo bla" nil file-notify--test-tmpfile nil 'no-message)
+
+              ;; Check, that the buffer has been reverted.
+              (file-notify--wait-for-events
+               timeout
+               (string-match
+                (format-message "Reverting buffer `%s'." (buffer-name buf))
+                captured-messages))
+              (should (string-match "foo bla" (buffer-string)))))
 
           ;; The environment shall be cleaned up.
           (file-notify--test-cleanup-p))
 
       ;; Cleanup.
-      (with-current-buffer "*Messages*" (widen))
       (ignore-errors (kill-buffer buf))
       (file-notify--test-cleanup))))