org-latex-verse-block: Fix regression from 3f60acff7

* lisp/ox-latex.el (org-latex-verse-block): Fix logic replacing sole
paragraph breaks according to the new template.
* testing/lisp/test-ox-latex.el: New test file.
(org-test-with-exported-text): New macro for testing export.
(test-ox-latex/verse): New test.
* mk/default.mk (BTEST_RE): Select the new test by default.

Reported-by: Juan Manuel Macías <maciaschain@posteo.net>
Link: https://orgmode.org/list/875ygk6a8z.fsf@posteo.net

lisp/ox-latex.el

@@ -4105,7 +4105,8 @@ contextual information."
 	      (replace-regexp-in-string
 	       "^[ \t]+" (lambda (m) (format "\\hspace*{%dem}" (length m)))
 	       (replace-regexp-in-string
-	        "^[ \t]*\\\\\\\\$" "\\vspace*{1em}"
+                (concat "^[ \t]*" (regexp-quote org-latex-line-break-safe) "$")
+	        "\\vspace*{1em}"
 	        (replace-regexp-in-string
 	         "\\([ \t]*\\\\\\\\\\)?[ \t]*\n"
                  (concat org-latex-line-break-safe "\n")

mk/default.mk

@@ -72,7 +72,7 @@ REPRO_ARGS ?=
 req-ob-lang = --eval '(require '"'"'ob-$(ob-lang))'
 lst-ob-lang = ($(ob-lang) . t)
 req-extra   = --eval '(require '"'"'$(req))'
-BTEST_RE   ?= \\(org\\|ob\\)
+BTEST_RE   ?= \\(org\\|ob\\|ox\\)
 BTEST_LOAD  = \
 	--eval '(add-to-list '"'"'load-path (concat default-directory "lisp"))' \
 	--eval '(add-to-list '"'"'load-path (concat default-directory "testing"))'

testing/lisp/test-ox-latex.el

@@ -0,0 +1,74 @@
+;;; test-ox-latex.el --- tests for ox-latex.el       -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2022  Ihor Radchenko
+
+;; Author: Ihor Radchenko <yantar92@posteo.net>
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Tests checking validity of Org LaTeX export output.
+
+;;; Code:
+
+(require 'ox-latex nil t)
+(unless (featurep 'ox-latex)
+  (signal 'missing-test-dependency "org-export-latex"))
+
+(defmacro org-test-with-exported-text (backend source &rest body)
+  "Run BODY in export buffer for SOURCE string via BACKEND."
+  (declare (indent 2))
+  `(org-test-with-temp-text ,source
+     (let ((export-buffer (generate-new-buffer "Org temporary export")))
+       (unwind-protect
+           (progn
+             (org-export-to-buffer ,backend export-buffer)
+             (with-current-buffer export-buffer
+               ,@body))
+         (kill-buffer export-buffer)))))
+
+
+
+(ert-deftest test-ox-latex/verse ()
+  "Test verse blocks."
+  (org-test-with-exported-text
+      'latex
+      "#+begin_verse
+lorem ipsum dolor
+lorem ipsum dolor
+
+lorem ipsum dolor
+lorem ipsum dolor
+
+lorem ipsum dolor
+lorem ipsum dolor
+#+end_verse
+"
+    (goto-char (point-min))
+    (should
+     (search-forward
+      "\\begin{verse}
+lorem ipsum dolor\\\\\\empty
+lorem ipsum dolor\\\\\\empty
+\\vspace*{1em}
+lorem ipsum dolor\\\\\\empty
+lorem ipsum dolor\\\\\\empty
+\\vspace*{1em}
+lorem ipsum dolor\\\\\\empty
+lorem ipsum dolor\\\\\\empty
+\\end{verse}"))))
+
+(provide 'test-ox-latex)
+;;; test-ox-latex.el ends here