I installed the patch tester and after a sucessull instal i can't apply any patch,, everything else works fine.
There is no error message just:

Message
There are no files to patch from this pull request. This may mean that the files in the pull request are not present in your installation.

The problem seems to be in
https://github.com/joomla-extensions/patchtester/blob/master/administrator/components/com_patchtester/PatchTester/Model/PullModel.php#L174

I investigated the problem and the problem in the diff url $pull->diff_url is a redirect to another URI.
Example: https://github.com/joomla/joomla-cms/pull/8645.diff to https://patch-diff.githubusercontent.com/raw/joomla/joomla-cms/pull/8645.diff

By forcing the follow location (follow redirects) in curl JHttpFactory $options[CURLOPT_FOLLOWLOCATION] = 1; it works.
See https://github.com/joomla/joomla-cms/blob/staging/libraries/joomla/http/transport/curl.php#L160-L163

My PHP (5.6.x) config has open_basedir enabled and that seems to be the problem.

An aditional note:
As of PHP 5.6+ curl follow location already work with open_basedir and safe_mode.
http://php.net/ChangeLog-5.php
Implemented FR #65646 (re-enable CURLOPT_FOLLOWLOCATION with open_basedir or safe_mode).

@mbabker can you check?

And, of course, thanks for all your work in Joomla