test: extract message-capture helper into testutil

Five test files hand-rolled the same scaffolding to capture the echo-area message: a nil-initialized var, a cl-letf on message, and a lambda that stored the formatted string. Centralize it as testutil-wttrin-with-captured-message, which binds the var and captures the last message shown.

Behavior is unchanged. The full suite stays green. Sites that mock message for a different reason are left alone: the ones that silence it with #'ignore, and the one that accumulates every message into a list.

6 files changed, 45 insertions, 55 deletions

diff --git a/tests/test-wttrin--display-weather.el b/tests/test-wttrin--display-weather.el
index bca6a6c..4cc4269 100644
--- a/tests/test-wttrin--display-weather.el
+++ b/tests/test-wttrin--display-weather.el
@@ -159,11 +159,8 @@ Empty string does not match ERROR pattern, so it's processed as data."
   (test-wttrin--display-weather-setup)
   (unwind-protect
       (progn
-        (let ((message-log-max t)
-              (message-displayed nil))
-          (cl-letf (((symbol-function 'message)
-                     (lambda (format-string &rest args)
-                       (setq message-displayed (apply #'format format-string args)))))
+        (let ((message-log-max t))
+          (testutil-wttrin-with-captured-message message-displayed
             (wttrin--display-weather "InvalidCity" nil)
 
             ;; Should display error message
@@ -176,11 +173,8 @@ Empty string does not match ERROR pattern, so it's processed as data."
   (test-wttrin--display-weather-setup)
   (unwind-protect
       (progn
-        (let ((message-log-max t)
-              (message-displayed nil))
-          (cl-letf (((symbol-function 'message)
-                     (lambda (format-string &rest args)
-                       (setq message-displayed (apply #'format format-string args)))))
+        (let ((message-log-max t))
+          (testutil-wttrin-with-captured-message message-displayed
             (wttrin--display-weather "BadLocation" testutil-wttrin-sample-error-response)
 
             ;; Should display error message
diff --git a/tests/test-wttrin--handle-fetch-callback.el b/tests/test-wttrin--handle-fetch-callback.el
index d4158ac..e50c61d 100644
--- a/tests/test-wttrin--handle-fetch-callback.el
+++ b/tests/test-wttrin--handle-fetch-callback.el
@@ -226,12 +226,9 @@
 (ert-deftest test-wttrin--handle-fetch-callback-error-network-shows-message ()
   "Network errors should show a specific message in the echo area,
 not leave the user guessing."
-  (let ((displayed-message nil))
+  (testutil-wttrin-with-captured-message displayed-message
     (cl-letf (((symbol-function 'wttrin--extract-response-body)
-               (lambda () nil))
-              ((symbol-function 'message)
-               (lambda (fmt &rest args)
-                 (setq displayed-message (apply #'format fmt args)))))
+               (lambda () nil)))
       (wttrin--handle-fetch-callback
        '(:error (error "Network unreachable"))
        #'ignore)
@@ -240,14 +237,11 @@ not leave the user guessing."
 
 (ert-deftest test-wttrin--handle-fetch-callback-error-http-404-shows-message ()
   "HTTP 404 should tell the user the location wasn't found."
-  (let ((displayed-message nil))
+  (testutil-wttrin-with-captured-message displayed-message
     (cl-letf (((symbol-function 'wttrin--extract-response-body)
                (lambda () nil))
               ((symbol-function 'wttrin--extract-http-status)
-               (lambda () 404))
-              ((symbol-function 'message)
-               (lambda (fmt &rest args)
-                 (setq displayed-message (apply #'format fmt args)))))
+               (lambda () 404)))
       ;; No :error in status — url-retrieve succeeded but server returned 404
       (wttrin--handle-fetch-callback nil #'ignore)
       (should displayed-message)
@@ -255,14 +249,11 @@ not leave the user guessing."
 
 (ert-deftest test-wttrin--handle-fetch-callback-error-http-500-shows-message ()
   "HTTP 500 should tell the user the weather service had an error."
-  (let ((displayed-message nil))
+  (testutil-wttrin-with-captured-message displayed-message
     (cl-letf (((symbol-function 'wttrin--extract-response-body)
                (lambda () nil))
               ((symbol-function 'wttrin--extract-http-status)
-               (lambda () 500))
-              ((symbol-function 'message)
-               (lambda (fmt &rest args)
-                 (setq displayed-message (apply #'format fmt args)))))
+               (lambda () 500)))
       (wttrin--handle-fetch-callback nil #'ignore)
       (should displayed-message)
       (should (string-match-p "service\\|server\\|500" (downcase displayed-message))))))
diff --git a/tests/test-wttrin-clear-cache.el b/tests/test-wttrin-clear-cache.el
index 8185c5f..784be4c 100644
--- a/tests/test-wttrin-clear-cache.el
+++ b/tests/test-wttrin-clear-cache.el
@@ -43,13 +43,10 @@
   "User should be told the cache was cleared."
   (test-wttrin-clear-cache-setup)
   (unwind-protect
-      (let ((displayed-message nil))
-        (cl-letf (((symbol-function 'message)
-                   (lambda (fmt &rest args)
-                     (setq displayed-message (apply #'format fmt args)))))
-          (wttrin-clear-cache)
-          (should displayed-message)
-          (should (string-match-p "cache cleared" displayed-message))))
+      (testutil-wttrin-with-captured-message displayed-message
+        (wttrin-clear-cache)
+        (should displayed-message)
+        (should (string-match-p "cache cleared" displayed-message)))
     (test-wttrin-clear-cache-teardown)))
 
 ;;; Boundary Cases
diff --git a/tests/test-wttrin-query.el b/tests/test-wttrin-query.el
index 396507b..4c4de87 100644
--- a/tests/test-wttrin-query.el
+++ b/tests/test-wttrin-query.el
@@ -102,20 +102,17 @@
   "When fetch returns nil, the user should see an error message, not a crash."
   (test-wttrin-query-setup)
   (unwind-protect
-      (let ((saved-callback nil)
-            (displayed-message nil))
-        (cl-letf (((symbol-function 'wttrin--get-cached-or-fetch)
-                   (lambda (_location callback)
-                     (setq saved-callback callback)))
-                  ((symbol-function 'message)
-                   (lambda (fmt &rest args)
-                     (setq displayed-message (apply #'format fmt args)))))
-          (wttrin-query "BadLocation")
-          ;; Simulate fetch returning nil
-          (funcall saved-callback nil)
-          ;; Should have shown error message (from wttrin--display-weather validation)
-          (should displayed-message)
-          (should (string-match-p "Cannot retrieve" displayed-message))))
+      (let ((saved-callback nil))
+        (testutil-wttrin-with-captured-message displayed-message
+          (cl-letf (((symbol-function 'wttrin--get-cached-or-fetch)
+                     (lambda (_location callback)
+                       (setq saved-callback callback))))
+            (wttrin-query "BadLocation")
+            ;; Simulate fetch returning nil
+            (funcall saved-callback nil)
+            ;; Should have shown error message (from wttrin--display-weather validation)
+            (should displayed-message)
+            (should (string-match-p "Cannot retrieve" displayed-message)))))
     (test-wttrin-query-teardown)))
 
 (provide 'test-wttrin-query)
diff --git a/tests/test-wttrin-requery-force.el b/tests/test-wttrin-requery-force.el
index d572348..171166d 100644
--- a/tests/test-wttrin-requery-force.el
+++ b/tests/test-wttrin-requery-force.el
@@ -63,15 +63,12 @@
   "When no current location is set, user should be told there's nothing to refresh."
   (test-wttrin-requery-force-setup)
   (unwind-protect
-      (let ((displayed-message nil))
-        (cl-letf (((symbol-function 'message)
-                   (lambda (fmt &rest args)
-                     (setq displayed-message (apply #'format fmt args)))))
-          (with-current-buffer (get-buffer-create "*wttr.in*")
-            ;; wttrin--current-location is nil (buffer-local default)
-            (wttrin-requery-force)
-            (should displayed-message)
-            (should (string-match-p "No location" displayed-message)))))
+      (testutil-wttrin-with-captured-message displayed-message
+        (with-current-buffer (get-buffer-create "*wttr.in*")
+          ;; wttrin--current-location is nil (buffer-local default)
+          (wttrin-requery-force)
+          (should displayed-message)
+          (should (string-match-p "No location" displayed-message))))
     (test-wttrin-requery-force-teardown)))
 
 (ert-deftest test-wttrin-requery-force-boundary-force-flag-does-not-leak ()
diff --git a/tests/testutil-wttrin.el b/tests/testutil-wttrin.el
index 7c71a84..e4e2e4e 100644
--- a/tests/testutil-wttrin.el
+++ b/tests/testutil-wttrin.el
@@ -111,6 +111,20 @@
                   (funcall callback nil)))))
      ,@body))
 
+;;; Message Capture Helpers
+
+(defmacro testutil-wttrin-with-captured-message (msg-var &rest body)
+  "Run BODY with `message' captured into MSG-VAR.
+MSG-VAR starts nil and is set to each formatted message string as `message'
+is called, so after BODY it holds the last message shown (or nil if none).
+Other mocks BODY needs can be set in a nested `cl-letf'."
+  (declare (indent 1))
+  `(let ((,msg-var nil))
+     (cl-letf (((symbol-function 'message)
+                (lambda (fmt &rest args)
+                  (setq ,msg-var (apply #'format fmt args)))))
+       ,@body)))
+
 ;;; Mode-line Cache Helpers
 
 (defun testutil-wttrin-set-mode-line-cache (data &optional age-seconds)