Fixes and additions: (#20)

- fix encryption bug #19, which was a regression
- added encryption unit test
- added debug logging here and there

Co-authored-by: Thomas von Dein <tom@vondein.org>

t/crypt.txtar

@@ -0,0 +1,37 @@
+# 
+# Copyright © 2025 Thomas von Dein
+# 
+# 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 <http://www.gnu.org/licenses/>.
+# 
+
+# encrypt something
+exec env ANYDB_PASSWORD=12345 anydb -f test.db set -e secret eshishinusan
+
+# retrieve it
+exec env ANYDB_PASSWORD=12345 anydb -f test.db get secret
+stdout eshishinusan
+
+# but has it really been encrypted?
+! exec env ANYDB_PASSWORD=8d8d8 anydb -f test.db get secret 
+! stdout eshishinusan
+stderr 'message authentication failed'
+
+# what about the listing
+exec anydb -f test.db ls -l
+stdout 'encrypted-content'
+! stdout eshishinusan
+
+# and the export?
+exec anydb -f test.db export -o -
+! stdout eshishinusan