Refactored.

test/ENABLE_POP3.bats

@@ -0,0 +1,15 @@
+@test "checking pop: server is ready" {
+  if [ $ENABLE_POP != 1 ]; then
+    skip
+  fi
+  run docker exec mail /bin/bash -c "nc -w 1 0.0.0.0 110 | grep '+OK'"
+  [ "$status" -eq 0 ]
+}
+
+@test "checking pop: authentication works" {
+  if [ $ENABLE_POP != 1 ]; then
+    skip
+  fi
+  run docker exec mail /bin/sh -c "nc -w 1 0.0.0.0 110 < /tmp/docker-mailserver-test/auth/pop3-auth.txt"
+  [ "$status" -eq 0 ]
+}