test: demonstrate incorrect -s option on mcron program

The option is supposed to be able to take an optional argument, but if the
argument is not supplied (should default to 8) then the test, rather than
failing, is skipped with a friendly message in the log file.  The proper fix
will come with an upstream patch to GNU Guile, and a future version of Mcron.

* tests/schedule-2.sh: new test, new file
* Makefile.am: make sure to run the new test file

Makefile.am

@@ -136,6 +136,7 @@ SCM_LOG_DRIVER = \
 TESTS = \
   tests/basic.sh \
   tests/schedule.sh \
+  tests/schedule-2.sh \
   tests/base.scm \
   tests/environment.scm \
   tests/job-specifier.scm \

tests/schedule-2.sh

@@ -0,0 +1,82 @@
+# schedule-2.sh -- Check mcron schedule output
+# Copyright © 2020  Dale Mellor <mcron-lsfnyl@rdmp.org>
+#
+# This file is part of GNU Mcron.
+#
+# GNU Mcron 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.
+#
+# GNU Mcron 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 GNU Mcron.  If not, see <http://www.gnu.org/licenses/>.
+
+source "${srcdir}/tests/init.sh"
+
+# Use UTC and SOURCE_DATE_EPOCH to get reproducible result.
+
+SOURCE_DATE_EPOCH=1
+export SOURCE_DATE_EPOCH
+
+TZ=UTC0
+export TZ
+
+LC_ALL=C
+export LC_ALL
+
+# Use current working directory to store mcron files
+XDG_CONFIG_HOME=`pwd`
+export XDG_CONFIG_HOME
+
+mkdir cron
+cat > cron/foo.guile <<EOF
+(job '(next-second) '(display "foo\n"))
+EOF
+
+cat > expected <<EOF
+Thu Jan  1 00:00:01 1970 +0000
+(display foo
+)
+
+Thu Jan  1 00:00:02 1970 +0000
+(display foo
+)
+
+Thu Jan  1 00:00:03 1970 +0000
+(display foo
+)
+
+Thu Jan  1 00:00:04 1970 +0000
+(display foo
+)
+
+Thu Jan  1 00:00:05 1970 +0000
+(display foo
+)
+
+Thu Jan  1 00:00:06 1970 +0000
+(display foo
+)
+
+Thu Jan  1 00:00:07 1970 +0000
+(display foo
+)
+
+Thu Jan  1 00:00:08 1970 +0000
+(display foo
+)
+
+EOF
+
+mcron -s cron/foo.guile > output-A
+diff expected output-A \
+    || skip_ 'The -s option is not fully functional; 
+this will be fixed with a future version of GNU Guile and then 
+a future version of GNU Mcron.'
+
+Exit 0