add test: check if cronfile has a valid syntax

Signed-off-by: casperklein <casperklein@users.noreply.github.com>

test/tests/test_general.py

@@ -12,11 +12,13 @@ def test_pihole_gid_env_var(docker):
     func = docker.run("id -g pihole")
     assert "456" in func.stdout
 
+
 def test_pihole_ftl_version(docker):
     func = docker.run("pihole-FTL -vv")
     assert func.rc == 0
     assert "Version:" in func.stdout
 
+
 # Wait 5 seconds for startup, then kill the start.sh script
 # Finally, grep the FTL log to see if it has been shut down cleanly
 def test_pihole_ftl_clean_shutdown(docker):
@@ -30,3 +32,14 @@ def test_pihole_ftl_clean_shutdown(docker):
     )
     assert "INFO: ########## FTL terminated after" in func.stdout
     assert "(code 0)" in func.stdout
+
+
+def test_cronfile_valid(docker):
+    func = docker.run(
+        """
+        /usr/bin/crontab /crontab.txt
+        crond -d 8 -L /cron.log
+        grep 'parse error' /cron.log
+    """
+    )
+    assert "parse error" not in func.stdout