Testing Email with a Mock MailSender

If you have an application which sends out email, you don't want your unit tests doing that too, so you need to use a "mock mail sender". You can create one by extending JavaMailSenderImpl and overriding the send method so that it doesn't really send an email. Here is an example:

import java.util.Properties;

import javax.mail.internet.MimeMessage;

import org.springframework.mail.MailException;
import org.springframework.mail.MailPreparationException;
import org.springframework.mail.javamail.JavaMailSenderImpl;
import org.springframework.mail.javamail.MimeMessagePreparator;

public class MockMailSender extends JavaMailSenderImpl {

  @Override
  public void send(final MimeMessagePreparator mimeMessagePreparator) throws MailException {
    final MimeMessage mimeMessage = createMimeMessage();
    try {
      mimeMessagePreparator.prepare(mimeMessage);
      final String content = (String) mimeMessage.getContent();
      final Properties javaMailProperties = getJavaMailProperties();
      javaMailProperties.setProperty("mailContent", content);
    } catch (final Exception e) {
      throw new MailPreparationException(e);
    }
  }
}

The mock shown above stores the email body into the mail properties object. This is a quick-and-dirty way of getting access to the content of the email just in case you want to check it in your unit test.

Here is the associated Spring Java-based configuration:

@Configuration
public class MailConfig {

  @Bean
  public JavaMailSender mailSender() {
    final JavaMailSenderImpl sender = new JavaMailSenderImpl();
    sender.setHost("mail.host.com");
    return sender;
  }

  @Bean
  public Notifier notifier() {
    return new Notifier(mailSender());
  }
}

The unit-test configuration:

@Configuration
@Profile("unit-test")
public class UnitTestMailConfig extends MailConfig {
  @Override
  @Bean
  public JavaMailSender mailSender() {
   return new MockMailSender();
  }
}

For more information about sending emails with Spring 3, see the documentation here.

Related Posts:
Spring 3 - JavaConfig: Unit Testing