Adding custom php file in wordpress theme

[admin]

I want to add an additional php file, for example test.php in my wordpress theme, and access it with url like

example.com/wordpress/test.php

When I place this test.php file in the theme directory, I can't access it.
So I how can I do that? It allows to access only if i place the test.php in the wordpress root, but i want to add the file in the theme directory instead of the root directory, which is at

wordpress\wp-content\themes\mytheme\test.php