How to configure subdomains for Apache2 on Ubuntu?

Question

I followed these instructions to configure subdomains for apache. I can access the subdomain using http://localhost/test though I cannot access it via http://test.localhost. How can I realize the latter?

# /etc/apache2/sites-available/test.localhost
<VirtualHost *:80>

    # Server name
    ServerName test.localhost

    # Document root
    DocumentRoot /var/www/test/

    # Custom log file locations
    ErrorLog  /var/www/test/logs/error.log
    CustomLog /var/www/test/logs/access.log combined

</VirtualHost>

Answer 1

As Mark B already answered correctly the problem was a misconfiguration in /etc/hosts. The correct configuration is:

# /etc/hosts
127.0.0.1     test.localhost