Installing wordpress in root as well as in subdirectory

We have a wordpress site which is runnung in root directory. Now we want to install same site with different database name in subdirectory for testing purpose.

STARTING POINT:
http://www.mywordpress.com   /var/www/
http://www.mywordpress.com/foldername   /var/www/foldername

Step 1:

Put same code in /var/www/foldername as in /var/www/ . Connect it with new database.

Step 2:

Change .htaccess file in /var/www/foldername as given below

# BEGIN WordPress

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /foldername/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /foldername/index.php [L]
</IfModule>

# END WordPress

At this point the configuration will not be working because the .htaccess directives at /var/www/.htaccess with be controlling all aspects of the URL so the directives at /var/www/foldername/.htaccess will have no bearing.

Step 3 :

The final step is to modify the default WordPress htaccess directives so that they will have control in for all variations of the URL.
Now change .htaccess file in /var/www as given below

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
Options +FollowSymLinks
RewriteRule ^/?foldername/$ /var/www/foldername/index.php [L]
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

Step 4:

Now login to your http://www.mywordpress.com/foldername/wp-admin/ section. Go to Setting->Permalinks.

Choose Post name in common setting.

Now it will work in root as well in subdirectory.