Email testing with Greenmail

When an application provides support for sending and receiving emails we need to be able to write test cases to automate the verification of this functionality. Green mail  is a great library for Implementing this functionality. Greenmail provide support for various mail protocols such as smtp, smtps, pop3 , pop3s , imap and imaps.

You can start a Greenmail server to listen with all these protocols enabled and listening on localhost with two lines of code.

        GreenMail greenMail = new GreenMail();
        greenMail.start();


When the server is started as above, the default ports of the above supported protocols are offset by 3000.

SMTP    : 3025    SMTPS  : 3465   POP3     : 3110   POP3S   : 3995  IMAP    : 3143  IMAPS  : 3993

However, if you start the server as above, more often than not, there will be a port conflict with some other program resulting in exceptions. Therefore you can configure the GreenMail server with the ServerSetup object with the protocol , binding address and port.

 ServerSetup setup = new ServerSetup(3025, "localhost", "smtp");
 GreenMail greenMail = new GreenMail(setup);

You can register a user to the server by using setUser method.

greenMail.setUser("user1@mail.com", "user1", "user1");

In order to receive mails from greenmail server object, waitForIncomingEmail method is available.

greenMail.waitForIncomingEmail(5000, 1);
Message[] messages = greenMail.getReceivedMessages();

In order to find more details, take a look at the source code at https://github.com/greenmail-mail-test/greenmail

Following is a sample on how to send a mail using java mail and receive it using greenmail with user authentication enabled.

import com.icegreen.greenmail.util.GreenMail;
import com.icegreen.greenmail.util.ServerSetup;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import java.io.IOException;
import java.util.Properties;

public class GreenMailTest {

    public static void main(String[] args) throws InterruptedException, IOException, MessagingException {
        ServerSetup setup = new ServerSetup(3025, "localhost", "smtp");
        GreenMail greenMail = new GreenMail(setup);
        greenMail.setUser("user1@mail.com", "user1", "user1");
        greenMail.start();

        final String username = "user1";
        final String password = "user1";

        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.transport.protocol", "smtp");
        props.put("mail.smtp.host", "localhost");
        props.put("mail.smtp.port", "3025");

        Session session = Session.getInstance(props,
                                              new javax.mail.Authenticator() {
                                                  protected PasswordAuthentication getPasswordAuthentication() {
                                                      return new PasswordAuthentication(username, password);
                                                  }
                                              });

        Message message = new MimeMessage(session);
        message.setSubject("Mail Subject");
        message.setText("Mail content");
        message.setFrom(new InternetAddress("user1@mail.com"));
        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse("user1@mail.com"));
        Transport.send(message);

        greenMail.waitForIncomingEmail(5000, 1);
        Message[] messages = greenMail.getReceivedMessages();
        System.out.println("Message length =>" + messages.length);
        System.out.println("Subject => " + messages[0].getSubject());
        System.out.println("Content => " + messages[0].getContent().toString());
        System.out.println("Done");
        greenMail.stop();
    }
}