ert-x: New `ert-with-test-buffer-selected' convenience macro

* lisp/emacs-lisp/ert-x.el (ert-with-test-buffer-selected): New
convenience macro that extends `ert-with-test-buffer' by displaying
the test buffer in a temporary selected window.  This makes it easier
to simulate user input in the body via `execute-kbd-macro'.
* test/lisp/emacs-lisp/ert-x-tests.el
(ert-test-test-buffer-selected/*): Add tests.

2 files changed, 44 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/ert-x.el b/lisp/emacs-lisp/ert-x.el
index 4436d0a4b16..fe291290a28 100644
--- a/lisp/emacs-lisp/ert-x.el
+++ b/lisp/emacs-lisp/ert-x.el
@@ -102,6 +102,35 @@ the name of the test and the result of NAME-FORM."
            (indent 1))
   `(ert--call-with-test-buffer ,name-form (lambda () ,@body)))
 
+(cl-defmacro ert-with-test-buffer-selected ((&key name)
+                                            &body body)
+  "Create a test buffer, switch to it, and run BODY.
+
+This extends `ert-with-test-buffer' by displaying the test
+buffer (whose name is derived from NAME) in a temporary window.
+The temporary window becomes the `selected-window' before BODY is
+evaluated.  The modification hooks `before-change-functions' and
+`after-change-functions' are not inhibited during the evaluation
+of BODY, which makes it easier to use `execute-kbd-macro' to
+simulate user interaction.  The window configuration is restored
+before returning, even if BODY exits nonlocally.  The return
+value is the last form in BODY."
+  (declare (debug ((":name" form) def-body))
+           (indent 1))
+  (let ((ret (make-symbol "ert--with-test-buffer-selected-ret")))
+    `(save-window-excursion
+       (let (,ret)
+         (ert-with-test-buffer (:name ,name)
+           (with-current-buffer-window (current-buffer)
+               `(display-buffer-below-selected
+                 (body-function
+                  . ,(lambda (window)
+                       (select-window window t)
+                       (let ((inhibit-modification-hooks nil))
+                         (setq ,ret (progn ,@body))))))
+             nil))
+         ,ret))))
+
 ;;;###autoload
 (defun ert-kill-all-test-buffers ()
   "Kill all test buffers that are still live."
diff --git a/test/lisp/emacs-lisp/ert-x-tests.el b/test/lisp/emacs-lisp/ert-x-tests.el
index 38698041102..63e7cd7608f 100644
--- a/test/lisp/emacs-lisp/ert-x-tests.el
+++ b/test/lisp/emacs-lisp/ert-x-tests.el
@@ -82,6 +82,21 @@
         (should-not (buffer-live-p buffer-1))
         (should (buffer-live-p buffer-2))))))
 
+(ert-deftest ert-test-with-test-buffer-selected/selected ()
+  (ert-with-test-buffer-selected ()
+    (should (eq (window-buffer) (current-buffer)))))
+
+(ert-deftest ert-test-with-test-buffer-selected/modification-hooks ()
+  (ert-with-test-buffer-selected ()
+    (should (null inhibit-modification-hooks))))
+
+(ert-deftest ert-test-with-test-buffer-selected/return-value ()
+  (should (equal (ert-with-test-buffer-selected () "foo") "foo")))
+
+(ert-deftest ert-test-with-test-buffer-selected/buffer-name ()
+  (should (equal (ert-with-test-buffer (:name "foo") (buffer-name))
+                 (ert-with-test-buffer-selected (:name "foo")
+                   (buffer-name)))))
 
 (ert-deftest ert-filter-string ()
   (should (equal (ert-filter-string "foo bar baz" "quux")