Add end-to-end Test

- Add an infrastructur to run local e2e tests.
- Add some tests.

e2e-tests/tests/20_simple_encrypt.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/bash
+
+echo "Simple: Test encryption for available certificate"
+
+# There is an authenticated certificate for bob in the cert store
+adduser --shell /bin/bash --disabled-password --gecos "" bob
+echo "test mail" | sendmail bob@example.com
+
+sleep 1
+
+if [ -f /var/mail/bob ] ; then
+  if grep -q "BEGIN PGP MESSAGE" /var/mail/bob ; then
+    RESULT_CODE=0
+  else
+    echo "no encryption detected"
+    RESULT_CODE=1
+  fi
+else
+  echo "no mail detected"
+  RESULT_CODE=1 
+fi
+
+deluser --remove-home bob
+
+exit $RESULT_CODE