SMTP server mock as a JUnit TestRule

MockSMTPRule.java

package com.chelonix.selenium;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import com.dumbster.smtp.SimpleSmtpServer;
import com.dumbster.smtp.SmtpMessage;
import com.google.common.collect.Lists;
import org.junit.rules.ExternalResource;

/**
 * A JUnit Rule which runs a mock SMTP server
 *
 * @see org.junit.rules.TestRule
 */
public class MockSMTPRule extends ExternalResource
{
	private int port = SimpleSmtpServer.DEFAULT_SMTP_PORT;
	private SimpleSmtpServer smtp;

	/**
	 * Creates a SMTP server listening on port 25.
	 */
	public MockSMTPRule()
	{
	}

	/**
	 * Creates a SMTP server listening on the given port.
	 * @param port the SMTP port
	 */
	public MockSMTPRule(int port)
	{
		this.port = port;
	}

	public synchronized int getReceivedEmailSize()
	{
		return smtp.getReceivedEmailSize();
	}

	public synchronized Iterator getReceivedEmail()
	{
		return smtp.getReceivedEmail();
	}

	public List<SmtpMessage> getReceivedEmailAsList()
	{
		return Lists.newArrayList((Iterator<SmtpMessage>)getReceivedEmail());
	}

	@Override
	protected void after()
	{
		smtp.stop();
		super.after();
	}

	@Override
	protected void before() throws Throwable
	{
		super.before();
		smtp = SimpleSmtpServer.start(port);
	}
}