public FtpSource ensureStarted() {
		FtpServerFactory serverFactory = new FtpServerFactory();
		serverFactory.setUserManager(new FtpDummyUserManager(remoteServerDirectory, "foo", "bar"));

		ListenerFactory factory = new ListenerFactory();
		factory.setPort(port);
		serverFactory.addListener("default", factory.createListener());

		server = serverFactory.createServer();
		try {
			server.start();
		}
		catch (FtpException e) {
			throw new IllegalStateException(e);
		}

		return this;
	}
A fixture that helps testing the ftp source. Creates a local FTP server and exposes a file
directory where files to be picked up can be added.

@author Eric Bottard
@author Franck Marchand
@author David Turanski
spring-xd-test-fixtures/src/main/java/org/springframework/xd/test/fixtures/FtpSource.java