You could just skip the 3 rules when the HTTP_HOST is test.mysite.nl e.g.
RewriteEngine On
RewriteBase /
#
# The following "3" rules do not apply to test.mysite.nl
RewriteCond %{HTTP_HOST} test.mysite.nl
RewriteRule .* - [S=3]
#
RewriteCond %{REQUEST_URI} !(\.|/$)
RewriteRule (.*)
http://www.mysite.nl/$1/ [R=301,L]
#
RewriteCond %{HTTP_HOST} ^mysite.nl$
RewriteRule ^/?(.*)$
http://www.mysite.nl/$1 [R=301,L]
#
RewriteCond %{REQUEST_URI} !^/production
RewriteRule ^(.*)$ production/$1 [L]