test/emacs: test saving of attachment containing 8bit octets

This test catches the case 8bit octets in an attachment gets converted
or lost when saving attachment to the file.
This test is marked known broken.

test/emacs

@@ -516,6 +516,33 @@ test_emacs '(let ((standard-input "\"attachment2.gz\""))
 	      (notmuch-show-save-part "id:cf0c4d610911171136h1713aa59w9cf9aa31f052ad0a@mail.gmail.com" 5))'
 test_expect_equal_file attachment2.gz "$EXPECTED/attachment"
 
+test_begin_subtest "Save 8bit attachment from within emacs using notmuch-show-save-attachments"
+test_subtest_known_broken
+
+add_message '[subject]="Attachment with 8bit chars"' \
+	'[header]="MIME-Version: 1.0"' \
+	'[content-type]="multipart/mixed; boundary=\"abcd\""' \
+	'[body]="--abcd
+Content-Type: text/plain
+
+Attachment follows:
+
+--abcd
+Content-Type: application/octet-stream; name=\"sample\"
+Content-Transfer-Encoding: 8bit
+Content-Disposition: attachment; filename=\"sample\"
+
+“¡ Hey ! It compiles ¡ Ship it !”
+
+--abcd--
+"'
+test_emacs '(notmuch-show "id:'"${gen_msg_id}"'")
+	    (delete-file "OUTPUT")
+	    (let ((standard-input "\"OUTPUT\""))
+	      (notmuch-show-save-attachments))'
+
+test_expect_equal "$(cat OUTPUT)" '“¡ Hey ! It compiles ¡ Ship it !”'
+
 test_begin_subtest "View raw message within emacs"
 test_emacs '(notmuch-show "id:cf0c4d610911171136h1713aa59w9cf9aa31f052ad0a@mail.gmail.com")
 	    (notmuch-show-view-raw-message)