if theme/tests/behat/behat_theme_{THEME_NAME}_behat_selectors.php
file exits, and has class with same file name then we will
call behat_theme_{THEME_NAME}_behat_selectors::register_moodle_selectors()
to register theme specific selectors. If they are different
then core then they will override

But in order to maintain smooth backwards compatibility, the logos
set in the themes themselves take precedence.

The function send_content_uncached() is meant to be used when serving
content which should not be cached by browsers/proxies. You will
use this in development mode, or when the request is malformed
but you need to return some fallback content which shouldn't be stored
under the URL it was requested from.

The function file_safe_save_content() should only be used for content
not stored in the file API. Good candidates for this are resource
which fit well in the localcache. The function tries to write the
content in the most atomic way as possible to prevent incomplete
writes or concurrent writes.

Use core functions that are faster for test file creation.
To support large requests for hashes, the core hash function
must support large hashes without recursion.  PHP has a default
recursion depth of 100 and long hashes don't support this.

Remove transactions as they create performance problems for larger
courses and doesn't introduce significant benefit for developers.

Performance changes meant the times were much faster, a reasonable
guess was taken on performance of an average machine.