Learning something more about Emacs tests

[Lele Gaifax]

Hi all,

I tried to extend test/automated/tabulated-list-test.el to cover Bug#22194
(that Eli quickly fixed in fb2eaf0ffc213fac170cff4814b7c93bd0c44c20, thanks!).

I understand that I'm probably wasting my time since the issue is closed, but
just for the sake of learning something more about Emacs testing, I persevered
another bit, trying to understand what I'm missing.  I'm sorry for the length
of this post, but hopefully some of you can shed some light on me... :-)


I basically installed the following patch:

  diff --git a/test/automated/tabulated-list-test.el 
b/test/automated/tabulated-list-test.el
  index 9aa62ee..49353a7 100644
  --- a/test/automated/tabulated-list-test.el
  +++ b/test/automated/tabulated-list-test.el
  @@ -28,7 +28,8 @@ tabulated-list--test-entries
     '(("zzzz-game" ["zzzz-game" "zzzz-game" "2113" "installed" " play zzzz in 
Emacs"])
       ("4clojure"  ["4clojure" "4clojure" "1507" "obsolete" " Open and 
evaluate 4clojure.com questions"])
       ("abc-mode"  ["abc-mode" "abc-mode" "944" "available" " Major mode for 
editing abc music files"])
  -    ("mode"      ["mode" "mode" "1128" "installed" " A simple mode for 
editing Actionscript 3 files"])))
  +    ("mode"      ["mode" "mode" "1128" "installed" " A simple mode for 
editing Actionscript 3 files"])
  +    ("foo-mode"  ["foo-mode" "foo-mode" "1234" "installed" " A simple mode 
for editing Foo files"])))

   (defun tabulated-list--test-sort-car (a b)
     (string< (car a) (car b)))
  @@ -59,7 +60,8 @@ tabulated-list--test-with-buffer
                       "       zzzz-game  zzzz-game  2113      installed   play 
zzzz in Emacs
          4clojure   4clojure   1507      obsolete    Open and evaluate 
4clojure.com questions
          abc-mode   abc-mode   944       available   Major mode for editing 
abc music files
  -       mode       mode       1128      installed   A simple mode for editing 
Actionscript 3 files\n"))
  +       mode       mode       1128      installed   A simple mode for editing 
Actionscript 3 files
  +       foo-mode   foo-mode   1234      installed   A simple mode for editing 
Foo files\n"))
      ;; Preserve position.
      (forward-line 3)
      (let ((pos (thing-at-point 'line)))
  @@ -69,14 +71,16 @@ tabulated-list--test-with-buffer
        (should (string= (buffer-substring-no-properties (point-min) 
(point-max))
                         "       4clojure   4clojure   1507      obsolete    
Open and evaluate 4clojure.com questions
          abc-mode   abc-mode   944       available   Major mode for editing 
abc music files
  -       mode       mode       1128      installed   A simple mode for editing 
Actionscript 3 files\n"))
  +       mode       mode       1128      installed   A simple mode for editing 
Actionscript 3 files
  +       foo-mode   foo-mode   1234      installed   A simple mode for editing 
Foo files\n"))
        ;; Check the UPDATE argument
        (pop tabulated-list-entries)
        (setf (cdr (car tabulated-list-entries)) (list ["x" "x" "944" 
"available" " XX"]))
        (tabulated-list-print t t)
        (should (string= (buffer-substring-no-properties (point-min) 
(point-max))
                         "       x          x          944       available   XX
  -       mode       mode       1128      installed   A simple mode for editing 
Actionscript 3 files\n"))
  +       mode       mode       1128      installed   A simple mode for editing 
Actionscript 3 files
  +       foo-mode   foo-mode   1234      installed   A simple mode for editing 
Foo files\n"))
        (should (equal (thing-at-point 'line) pos)))))

   (ert-deftest tabulated-list-sort ()
  @@ -88,6 +92,7 @@ tabulated-list--test-with-buffer
      (let ((text (buffer-substring-no-properties (point-min) (point-max))))
        (should (string= text "       4clojure   4clojure   1507      obsolete  
  Open and evaluate 4clojure.com questions
          abc-mode   abc-mode   944       available   Major mode for editing 
abc music files
  +       foo-mode   foo-mode   1234      installed   A simple mode for editing 
Foo files
          mode       mode       1128      installed   A simple mode for editing 
Actionscript 3 files
          zzzz-game  zzzz-game  2113      installed   play zzzz in Emacs\n"))

  @@ -103,6 +108,7 @@ tabulated-list--test-with-buffer
        (should (string= (buffer-substring-no-properties (point-min) 
(point-max))
                         "       zzzz-game  zzzz-game  2113      installed   
play zzzz in Emacs
          mode       mode       1128      installed   A simple mode for editing 
Actionscript 3 files
  +       foo-mode   foo-mode   1234      installed   A simple mode for editing 
Foo files
          abc-mode   abc-mode   944       available   Major mode for editing 
abc music files
          4clojure   4clojure   1507      obsolete    Open and evaluate 
4clojure.com questions\n"))
        ;; Again

that recreates the conditions I met (without breaking existing tests :-)

Then I added the following new test:

  (ert-deftest tabulated-list-visual-move ()
    ;; See Bug#22194
    (tabulated-list--test-with-buffer
     (goto-char (point-min))
     (skip-chars-forward "[:blank:]")
     (skip-chars-forward "[:word:]-")
     (backward-char)
     ;; now the cursor is on the ending “e” of “zzzz-game”
     (funcall-interactively 'next-line 3)
     (funcall-interactively 'next-line)
     (should (equal (line-number-at-pos (point)) 5))))

To my surprise, this test passes, either before or after Eli's fix. I tried
several variants in the way I call the next-line function, but either moving
one line at at time or in two steps like I did above, I was not able to
reproduce the initial bug case.

Even executing it interactively, there is some "subtle" difference in hitting
the “n” key (bound to next-line) and doing that with “M-: 
(funcall-interactively 'next-line)”.

*Before* Eli's fix, in the latter case after the second evaluation the cursor
ends at column 1 (ie just before the package name) and stays there in the
succeeding evaluations. *After* the fix, it goes at column 7 (that is, one
space after the name “mode”) and stays there.

On the other hand, using the “n” key to invoke it, before the fix it exhibit
the behaviour described in the bug report, while now it honors the goal-column
(or something similar): if the package name on the current line is longer than
the first one, the cursor stays at the initial column.

What am I doing wrong? How can I programmatically exercise the next-line
function retaining the interactive behaviour?

Thank you for any hint,
bye, lele.
-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
address@hidden  |                 -- Fortunato Depero, 1929.